"This no more resembles that than something unlike something else resembles that." - Loosely quoting PHNC
1. The conference owns the television rights of all conference home games of each conference member. If Texas decided to leave for the ACC, the Big 12 would own the rights to all Texas conference home games until the GOR expired. All Texas' ACC road games against ACC teams would not be included in the Big 12's GOR's as far as I understand it. That means Texas and the ACC would not get TV revenue (from the Big 12 GOR) from 4 conference games (in Austin) per football season until the Big 12 GOR expired.
2. The ACC could pay "fair market" value for all Texas conference homes games (ACC games in Austin) to the Big 12 until the GOR expired or the ACC can buy out the Big 12's GOR's for all Texas home conference games (which would be expensive).
The way Texas can get out of the Big 12 GOR agreement is:
1. Texas, along with Oklahoma, Oklahoma State, and Kansas (using OU, OSU, and KU as examples) could leave the Big 12 together and leave the Big 12 at 6 members. At 6 members, the Big 12 would lose its auto-bid for all sports. At 6 members, the Big 12 would have to find 1 member just to qualify for an automatic bid in all sports. The Big 12 would have to get to 12 football members to qualify for a championship game (which many feel one day will be a requirement to get into the new BCS playoffs). It is likely the Big 12 would replace the 4 departing members and preserve their GOR, but the question is how much damage would those 4 departing schools have on the original GOR agreements. Would the Big 12's TV deal be greatly reduced (how much money would they lose?) and would the Big 12 drop out of the Power 5? All that could invalidate an existing GOR agreement. That's why I think Texas and Oklahoma really don't want 12 members. The smaller the membership, the better chance of having enough members depart and thus invalidating the GOR.
IMHO, Texas, going Independent for football, would not get them out of their present GOR agreement with the Big 12 if they joined the ACC in the same manner as Notre Dame did. Yes, it would be difficult to have Texas lose their TV rights to their home games since they are not in a conference. Basically, every home game would be an non-conference game which the Big 12 would not have the rights to. If Texas joined the ACC and played 5 ACC teams per season (like Notre Dame's agreement), then is it possible that the Big 12 would get the rights to those 2 or 3 ACC opponent games in Austin each season since Texas plays all its other sports in the ACC? That's where things get confusing. The only way Texas could possibly get out of their GOR agreement with the Big 12 is if they became an Independent in all sports and even that could get messy when they play any home football games against teams from the ACC, Big 10, Pac 12, and SEC.