The problem is, as I see it, that no two situations are going to be the same. There simply can't (and won't) be a single document that will govern all fan films equally, because Paramount/CBS isn't a governing body, it's a corporation. If one fan film gets away with something, good for them. It doesn't necessarily follow though that if Paramount cracks down on you (the general you) that they will do same on everyone else.
They can do whatever they want in this department and we have to just like it or love it.