Thanks for the feedback everyone.
There will be a backsplash going up (I'm doing that myself later on) so that should cover things if they cut in to the wall. There is a small exposed space on the side of the counter between the counter and the wall, that won't be covered by the backsplash. Its out of the way, but still I can't imagine that they would be able to cut into the wall cleanly enough so that you wouldn't be able to tell in that spot.
As far as pulling the other side out, there's really no gap at the wall now, so I think they'd have some room to move it. The problem is that its one big 'L' shaped piece, so I don't think they can pull it out without skewing the way the whole thing sits on the countertop.