Along with Texas, Florida, and California; it also sits on the Kentucky border, giving them access to some SEC recruiting grounds (so long as Cincinnati keeps doing well).

I don't think it is coincidence that the Big 12 offered schools in 3 of the prime recruiting areas of the US.

I'm not sure what to think about Houston — they have a large alumni base but that has never translated into a large fan base for their sports teams. Also, as you noted, the alumni tend to be "regional" — mostly in the Houston area — meaning they don't have the same pull in other areas like Texas and A&M. It will be interesting to see how the three schools are able to build fan bases.

I'm also not sure why Oklahoma would be like Nebraska. Nebraska was doing lots of Texas recruiting and basically lost that area, when they left the Big 12. By contrast, Oklahoma football is much like Texas — in the idea of "Friday Night Lights" being a big deal. Combine that with a large number of Oklahoma alumni living in Texas, Oklahoma's campus being as close to Dallas as Texas is, and still being in a conference with Texas and getting back in a conference with A&M — there is no reason to think that Oklahoma will have any more issues recruiting Texas than they currently do against SEC and other schools.