Despite being conference foes, Cal, Arizona, and Washington have never sold as many tickets for a home game against Utah as they did for each of their most recent home games against BYU. And those games were against multi-loss, mediocre BYU teams.
UCLA and Oregon State have each only once sold more tickets for a home game against Utah than for their most recent home game against BYU — and each was ranked #8 and undefeated at the time. Every other of their multiple Utah games sold fewer tickets than their BYU games.
This is all during the independence era.
Even after almost a decade of Utah's Pac 12 membership, Pac 12 fans apparently would rather watch their team play BYU than Utah.