These are some of the teams that queue off the top of my head on a pretty regular schedule on Pot5 in no order:
Clutch, Hostile Takeover, PKers, Ubique, LD50, S Key, Casual, I AM LEGEND, Nuff Said, Blueprint, The Watchmen, Infinite Darkness
I know I'm missing a few new start up guilds, but in total that brings the RWZ scene to around 15 teams potentially queuing at any given night. I'm not saying that all of the teams I listed could beat MVP, this post isn't about what team is better than said team. However, most of the teams on this list trade wins/losses quite frequently as the skill gap on Pot 5 in the rated scene is far less wide than that of Bastion. You can't walk into a RWZ expecting a "free win" because most likely it's going to be against a decently skilled team.
From a logical standpoint, it wouldn't make much sense for any rated team on Pot5 to transfer to the Bastion with the intentions of playing 3 of your top guilds, those being MVP, Synergy and Don't Panic, when the competition here is pretty great.
I dunno, the only reason I could see a Pot 5 team transferring is to have a chance to play Hey I'm MVP for a couple weeks, and then transfer back once the desire comes again to play more than 3 coherent guilds.