Cincinnati just got a safety from Alabama. UConn got a linebacker for Notre Dame. Houston got a 4 star running back transfer from Texas as well as a 4 star Safety from Texas A&M and a 3 star safety from OSU.
Colorado St. got a 4 star WR from Auburn and a 3 star defensive end from Arizona St. San Diego St. got a 3 star running back from Nebraska and a 3 star guard from Oregon.
There are plenty more examples of talented players transferring to MWC or AAC schools. There are many reasons why BYU wouldn't join the AAC or MWC, but the ability to get quality transfers (or recruits) is not one of them.