Interesting question. I did a quick search, and this is really all I could find:
http://www.hrc.org/blog/entry/whats-in-the-aca-for-transgender-peopleThough, it was a quick search; but it sounds much like what you said, it's mainly non-discriminative, in that coverage cannot be denied if it's available to others. And vaginoplasty (or, 'vaginal rejuvenation' for cis-females) looks to be considered elective. So I'd imagine it's not in any insurance plan, regardless of trans- status.
Something that was interesting in the HRC page, though, is that California, Colorado, Vermont, DC, and Oregon are "[putting] new rules are in place to eliminate many transition-related exclusions, and expect to see more states join this trend in the coming years."
That last part sounds pretty hopeful. It would be nice for the hefty premium on my individual-payer policy to go towards something helpful...