Yeah, I don't think Texas was ever in serious play for the Pac-12, while A&M and OU would be big boons, I don't think they move over without Texas to the Pac-12 (they would for SEC). Due to how small a state Oklahoma is, I believe OkSt and OU were also worried about hurting their recruiting in Texas (I know they did well there in the Big 8 era, but Texas never really became wide open recuiting wise until A&M left for the SEC).There was political pressure to stay in the Big 12 no doubt. But they knew they would make (at the time a lot) more money in the Pac. The fight they had with the Pac 10 was regarding tier 3 rights. They knew they had a good thing going with LHN and didn't want to lose that for a conference network unless they were going to make more from that, which nobody outside the Big 10 was. Actually I'm not even sure the Big 10 was, LHNs contract was a disaster for ESPN.
I'm a Longhorn fan (just grew up watching VY and its not like Canada has NCAA teams to cheer for). While I do remember talk of the Pac-16 at the time after Nebraska and Colorado left, I actually remember stronger talk about Texas potentially going independent if the LHN was a massive success, as they could demand huge numbers individually for their Tier 1 and tier 2 rights.