I think you are incorrect in your assessment of the relationship of BYU to the Church outside of the state of Utah. The VAST majority of active kids in my stake want to go to BYU. I would invite you to go to our seminary graduation this Sunday. It shouldn't be this way but students are almost embarrassed if they are not going to BYU.
As far as fans, I ordered about 200 tickets for my ward (and some friends in our stake) to the TCU games the past few trips to Fort Worth. I would guess that my stake had well over 1000 in attendance. Multiply that by the 10-12 stakes down here and you will see why we had nearly half the fans there in 2006. The TCU phone ticket guy complained about all the BYU fans ordering tickets and then said "You aren't one of them are you?".

Anyway, that is my experience. It does not mean it is repeated in every area. There are some Ute and other fans here but BYU is the number one draw in our stake.