I think, although I'm not sure, that when we moved to vBulletin we migrated accounts over from the previous platform (what that was, I can't recall now) and we brought post counts across too. However, at some stage a script was run which updated NSC's post counts in line with actual posts...
We moved platforms on a number of occasions, but we've been on vBulletin since July 2003. I do keep looking at Xenforo, which has taken a lot of market share away from vBulletin, and comes with some advantages such as being mobile responsive out of the box and a better notification system, but...
I think there are real advantages when it comes to scale. Although each micro-site may be pretty small, they all add up to a pretty significant whole. They'll be able to sell advertising directly covering the whole network which is considerably more lucrative than what NSC, for example, is able...
There's still a network a bit like rivals called FootyMad, so the model must work to some degree...
http://www.footymad.com/brighton--hove-albion/
The forum is a bit quiet though!
http://boards.footymad.net/forumdisplay.php?f=95