I don't have your insurance but I work for a different insurance company. Here is how it works and you should not have any issues.
1) find out what the clinical criteria is for your plan. Specifically what BMI and comorbity requirements they have. Any other requirements.
2) the FEHB proffesional claims (doctor time) and facility claims (hospital) are processed seperatly. You want to make sure that both are contracted with your plan.
3) ask for a checklist that your provider must complete prior to submitting your pre - authorization request.
If you ask lots of questions. Write down who and when you talk to people if they deny that information will help you with an appeal. Don't be afraid to ask for an appeal based on bad information. That is why most appeals are won.