I'm a teacher in Tx and I have TRS BCBS too. I'm not sure if every district has the same coverage though. Anyway, my wife (also a teacher) had the Sleeve last year and I will have it in June. Here was the catch - an additional $5000 co-pay towards the cost of the surgeon's fee was a requirement. This $5000 was not counted towards deductible or out of pocket max. Maybe you can find a surgeon who won't charge more than $5000 for services and you could save money that way.
Approval via Houston's Dr. Spiegel was less than six weeks. Requirements were a high enough BMI (not sure of the minimum number required), history of failed weight loss attempts, cleared by a psychiatrist, cleared by nutritionist, and cleared via initial consultation with the doctor.
Hope this helps.