As I understand it, crews are assigned to Pac 12, WCC, WAC, MWC, etc games by the Western Officiating Consortium or something like that. And the head of that organization as of a couple of years ago was connected somehow to the Pac 12. Director of officials i think. His name is Bobby Dibler. I think he doubles as coordinator of refs for the WCC. The way college refs are assigned is really weird to me.