Simply put, they used trades. It's not collusion if it's trades, because trades have to be balanced. Balanced trades aren't one-way streets like collusion is (that is, a balanced trade doesn't have a clearly improved team and a clearly weakened team).
Just once, juuuuuust once, I wish some of those "If I don't get my way and get so-and-so penalized/banned for this clear waaaahtheybeatmyteam, I'm quitting GLB!" whiners would keep their word and quit the game. They never do.
Oh, and I visited Webster just a few days ago. My grandmother lives there.
http://www.ci.webster.ny.us/It's a nice place, but they didn't say anything about collusion, morals, cheating, illegal or ban.