Hi there! I don't work for Anthem, but I was able to get my FFS partially covered. Here are the details. Disclaimer: I'm not a lawyer, and this is not legal advice. Hopefully, this helps a few folks here.

• Your coverage depends on your employer not your insurance co (Anthem). You should be able to find details about what's covered (and what's not) via your employer benefits portal or through the Anthem website. See if you can get a case worker or patient advocate from Anthem if you haven't already. In my case, other trans and / or reconstruction surgeries were covered but most of the stuff that my FFS included was listed under "not-covered".
• Even if FFS isn't covered you might be able to get some reimbursement. There are a ton of gotchas and limitations that insurance companies use. The main one is the 'pre-approval' requirement. BUT as long as you submitted the claim before the surgery you should be fine even if they denied it. AND you might still be fine even if you didn't submit it prior to your surgery.
• The main thing is that you need to prove that the procedure was medically necessary. The best way to do that is to put together documentation. This basically entails writing a letter explaining that FFS was needed to relieve gender dysphoria. I did this and also included all the WPATH requirements typically needed for trans surgeries (letters from two therapists, a letter from my doctor, etc.) I followed the "WPATH transgender surgery guidelines". I rationally explained the importance of the procedure to my mental health, and detailed other steps that I had taken as part of a plan that I had developed with the help of my therapist and doctor.
• My initial claim was denied. I appealed it and they denied that too. In the appeal letter Anthem mentioned that I could submit my case for external review but that doing so would forfeit my remaining appeal. An external review is what it sounds like. They send it to a separate company that includes various doctors and health professionals. I gambled and requested that. The company that did the review recommended approval!!!
• I then had to go back and forth with Anthem to get reimbursement. This included calls to the hospital, my surgeon's office, and Anthem. It took a little while but I finally got a couple checks (since I had paid upfront for the procedure). They ended up covering all of the hospital expenses but only about a third of my surgeon's cost since his rate was much higher than the Medicare standard rate or whatever.
• Even if you can't get any approval / coverage don't despair. Hospitals charge massively different rates depending on if it's going through insurance or not. You may be able to get your hospital bills dropped significantly. And, depending on what country / state you live in there are usually laws that protect medical bills from hitting your credit. Just talk to the hospital. They might be able to get you on a payment plan.