That seems odd to me. I grew up in the Deer Valley Stake and have lived in Surprise. Sure we were ASU fans but BYU football was huge. Up until I moved to Lehi a couple years ago, Saturdays in Fall were all about a huge gathering of Elders to one of our homes to watch the BYU game.
Regarding Ute fans...we had one family in the Ward. I never cared about Utah and did not follow them.
If you're LDS and grew up outside Utah, BYU sports was what it was all about.
I do remember going to see BYU play ASU in the 90's at Sun Devil Stadium. I was torn at first who to root for. That ceased when all the haters in the south end zone got me pumped up. I was cheering for BYU from that point forward. I still cheer for ASU (I'm alumni) but I consider myself True Blue now.