I think a cheating team will get caught soon or later. Especially if they get too high in world ranking or country ranking.
I'm pretty sure about everyone in my country (or, at very least, my opponents) have checked my transfers when I became champion last season. Also, I'm doing the same now that another team is taking my place. And if anything is suspected, it is reported to local GM, which, in turn, will check in depth. I guess you get the point.