If you get someone who doesn't know the policy, then it's possible. I was pre-op and brought in all kinds of documentation to get it done. Court order for name/gender marker change, therapist/psychiatrist's letter, and a letter from my endo as well. Got it done, no problem. I'm now post-op so I'm not worried about it getting reverted back, if that would even happen.
I consider myself lucky and glad I got someone open-minded (in my small, conservative town). Won't work for everyone though, especially in cities with a larger trans population. You could always try it and see. The worst they can do is tell you that you have to have surgery first.