For just as many times as people are hammering in that we heard they weren't canonical, I had heard the exact opposite said.
It was said exactly once that I know of that the comics were canonical -- Orci said so in what was evidently a joking manner when an interviewer was pressuring him to say it and he evidently just gave in to shut the guy up (and really, it was deeply obnoxious and unprofessional of the interviewer to try to browbeat his subject into agreeing with his personal wishes). Orci retracted the statement the very next day.
I was merely pointing out that we have seen how easily stories in the EU can be washed away by the next film. There's just no keeping it all together. Not even if you adopt the "big strokes" approach. It's going to get destroyed, eventually, by official on screen stories that say with no ambiguity that "things didn't happen that way."
Yes, and that's true even of tie-ins that are called canonical, like the
Star Wars EU. Because ultimately using the word that way is inaccurate. The canon, by strict definition, is the original body of work
as distinct from tie-ins and fanfiction. The word was originally used in Sherlock Holmes fandom specifically to mean those stories that were
not pastiches or derivative works. There will always be a distinction between the canon -- the core work -- and the derivative works like tie-ins. Tie-ins can be
consistent with the canon -- which is what we usually refer to as "canonical" as a shorthand -- but it's a mistake to believe they're in any way equivalent to the canon. They are separate and subordinate, and if the canon ends up evolving in a way that would require leaving its "canonical" tie-ins behind, then that's what it will do.
What would really be needed is a BS filter. Someone specifically there to keep track of things and make sure, at least generally, it all held together. The problem is it would tie the hands of the comic writers pretty much right off. If you follow Kirk's dialogue from STID for example, the Star Trek Game pretty much can't happen, a number of the comics can't happen as they are, either. Because according to STID, nobody died under Kirk's command for his first year.
There absolutely are people whose job it is to make sure it all holds together -- the attentive and talented folks at CBS Licensing who make sure all the tie-ins are consistent with canon. But as you say, requiring it to go the other way around would tie the hands of the canon's creators, and that makes no sense. Tie-in creators being restricted by canon makes sense -- after all, the whole reason our work exists is to follow the lead of the canon, to support and reflect it. But by the same token, it would make no sense for the creators of the source work to be bound by what the tie-ins do. They're free to draw on it if they choose, but it's always their choice, because it's their universe. We're just borrowing it.
So there will never be perfect consistency. Tie-ins can be compatible with canon... until they aren't. That's the best you can get.
With regards to the video game as canon, I think Christopher pointed out that that really cannot be counted. A video game, by its nature, is far more fluid, with multiple endings, character arcs and choices that will engage the player. Even Halo did a novelization of the original Halo game, allowing for the "official" events to happen while letting players have their freedom.
No, I wasn't saying that was actually, officially the case, just that it's the way it seems to me. There are instances where computer games
are considered canonical within a franchise's universe, such as with
Defiance, which was created to be a multimedia TV/game franchise. The events of the MMO game are treated as "real" in the show's universe and are frequently referenced in the show. But it's just the broad strokes of the events going on in the game, rather than the specifics of how individual players interact or move through the game. It seems to me that the missions are really just about running or driving to a certain place and shooting enemies that get in the way, and then when you finally reach the target site, a bit of story happens or you acquire the object you were looking for. So the overall flow of the story is going to be the same for pretty much every player. It's just the details that differ -- what happens between plot points and what character is experiencing the plot points -- and that throws me because I'm a detail-oriented person. It seems more reasonable to me that the game should be a simulation based on actual events, with those underlying events being canonical.
(Sort of like how Roddenberry's ST:TMP novelization hinted that TOS had been an "inaccurately larger-than-life" dramatization of Kirk's "real" adventures. They happened, just not quite in the way we were shown.)
Not so, because we've seen before that a single present timeline can be affected by more than one possible future. For instance, Voyager's timeline was affected by the future in which Kes stayed with the ship and Seven never joined ("Before and After"), the future in which the ship was destroyed in a slipstream experiment ("Timeless"), and the future in which the ship took 23 years to get home and Seven died ("Endgame"). Plot the timelines and you'll see travelers from multiple different futures traveling back into the same single timeline, with the same set of characters having their lives affected by events from multiple incompatible futures.
I'm not so sure that the three examples you list are that dissimilar to what Nero did - and in all cases probably led to a similar outcome, with the splintering of a new timeline being the end result. After all, the only reason it seems to be a "single" timeline is because we (the audience) stick with a particular sequence of events. With rare exceptions we are not privvy to other realities or outcomes, so naturally would not perceive them as the "real" timeline.
But from the perspective of the characters we did follow, their continuous worldlines were affected by travelers from multiple possible futures. Ultimately, with spontaneous quantum branchings happening every moment,
any "timeline" is simply going to be an arbitrary set of selections among the various branchings. But once you've defined a continuous path through the multiverse as a timeline, it is then valid to say that that timeline can be visited by travelers from multiple separate futures. So yes, if Kirk Prime and Kirk Alternate (we need a better name for that universe) both went back to before 2233, they definitely could meet and interact within the same single timeline. I see no reason that shouldn't be the case.