I think you are right too. If this is does happen would Tech then get the second BCS bid for the Big 12 because they beat Texas h2h or would it go to the bcs rankings?
Good question. I don't know the definitive answer but my best guess is that the only team with any BCS right, as it were, is the BIG-12 champion.
For instance, last season Oklahoma, as BIG-12 champion, went to the Fiesta Bowl and played a game I'd rather forget. The Orange Bowl chose Kansas over Missouri, even though Missouri beat Kansas heads up. At that point, it was obviously up to the BCS bowls as to which BIG-12 team(s) they wanted to choose.
With regard to who the BCS would choose between Texas and Texas Tech if OU were to with the BIG-12 South berth, it would largely depend on which team would bring the most fans to the host city, and which team would generate the largest TV viewing audience.
I hope this helps.