I wouldn't put it past them, but it sounds like something that would not be worth the risk. I doubt they would gain much by trying to keep tabs on them aside from knowing that they are 'opposers.' Their congregations would have publisher cards, and maybe they get a copy of those, along with any files that the local elders have.
Going any further than that would require work that I doubt the GB wants to do, and that they would not want to delegate. Set a loyal brother to the task of checking up on apostates, and before long you might have a fresh apostate on your hands.