FEP Blue TX does not do predetermination so no way to know till post op

Does anyone have expereince with an insurance company that does not do predetermination of payment? FEP Blue of Texas states they do not.  All paperwork has to be submitted post op. Their policy  states RNY is covered, lap band is not.  I thought great it says it is covered, so I called to make sure befoe I even saw the surgeon. It was confirmed on my phone call, yes it is covered, just need an adequate letter of medical necessity. Now, when I went to my pre op appt last spring the office staff for the surgeon cautioned me that FEP Blue TX has the option to use BCBS TX policy as a guideline. Long story short, I kept getting a "we cover it" reply, but the office was getting a "we may require the BCBSTX policy guidelines which involves a 12 month MD/nut diet, five year documented hx morbid obese, detailed letter medical necessity, plus others. I finally asked the nane of the person they spoke with, spoke with her and heard the same thing the office staff was hearing.  I got the website link, looked it up and found the multiple pages of requirements by BCBS TX.  Anyway I have been doing the diet thing, gathering the medical records for five years, rewriting the letter of medical necessity to get in all the requisite details, etc.  The totally frustrating thing is the lack of predetermination. I mean there is no way I can afford to pay for this surgery as am unemployed, living off savings. The surgery is directly related to my being more employable. The surgeon actually became involved not just office staff and will let me go ahead with surgery after six months of the diet, along with all the other criteria. So I get to have the RNY in Nov or Dec this year. I would love to hear from anyone with knowledge about this issue of not doing predetermination. thanks, Karen Martin