Are you doing the rear tire installation? Or is a shop doing it? If the rear tire was wearing evenly before, then most likely it was 'aligned' properly to begin with and when the shop (or you) do the rear tire swap (if done properly) the wheel alignment and belt tension should be right where it was before dismounting the wheel.
Laser alignment is of the front wheels. Maybe Joe Meyer can clarify this, but I believe the actual alignment they do is of the front wheels only. Not to say they don't check to make sure the belt is tracking okay on the rear wheel before doing the front wheel alignment, but they are two different things.
I hope this answers the question you seem to be asking.
Joe Meyer is the expert; whatever he says, believe it.
Go to this link for more info on dealers using the Rolo system;
http://www.spydercomfort.com/dealers.htm