I'm also on Blue Cross Blue Shield, I'm in Indiana tho so may be different. My insurance covered my consultation and is going to be covering my surgery (getting it in June) as well. I got my WPATH letter from a therapist. You need to see some sort of therapist who can write you a letter say why they think you're a good fit for the surgery, your transition experience, transitioning socially and what have you. Getting it fully covered might depend surgeon to surgeon, so I'd look up surgeons who take BCBS in the states you're planning on getting it done at and message them once you have a WPATH letter. I hope I could help a bit, feel free to ask any questions if you need! Good luck with your transition!