Is there is still a prime time line? It would depend on who had change the time line. If you went back in time and change events that had happen to you? Then when you travel back to your original starting date. You would had created a new time line and the original one would no longer exist.
But if someone else went back in time and change your past? Then the original time will continue on as is, but there will be a new time existing as well.
I dunno. The movie "First Contact" showed what happened to the original timeline when someone else went back in time and changed the past. (It doesn't continue on as-is.) It was only fortuitous that the E-E was protected by a time bubble. The same could be said also for "The City on the Edge of Forever" where McCoy aka "someone else" went back in time and altered history and the landing party was insulated from the changes by the Guardian.
The only times when the original timeline/continuity stays "relatively" intact is when someone else goes back in time is when the "someone else" was already predestined to do what they were going to do or it was spelled out that they were hopping dimensions / universes (continuities).
In AbramsTrek, it sounds like their starting "prime" continuity is different than what we know of regular TOS or even TNG continuity. There are some abilities that "prime" Spock appears to lack, most noticeably his desire to return back to his original universe or effect time-travel to undo Nero's damage. IMHO, of course.