BYU has continued to play them up until the inclusion in the Big 12 and with schedule crunching had to eliminate basically any long scheduled series (BSU, USU). That's not to mention that when BYU went Independent before that there was a plan to return to the WAC and BYU was making the plans with USU. I wouldn't be surprised if BYU schedules them again in the future. Utah on the other hand has basically almost refused to even acknowledge their fellow state school exists and up until this year, had refused to play them after losing up in Logan over a decade ago.

I have a cousin who married an Aggie and when I first met him he would talk about how much he hated BYU but I think with time I've been able to get through to him that his beef should be with Utah and not BYU. BYU has been regularly playing them in basically all sports unlike Utah. He seems to have softened his stance on BYU in recent years.