insurance is a tricky thing to navigate. MOST policies have specific exclusions for GID-- SRS and FFS are "cosmetic" and therefore unnecessary. You would have to check on the specific policy you're looking at purchasing. Gender-related treatment can be covered by a huge variety of insurance carriers, but it's usually at the request of the group purchasing insurance. So not all carriers will cover GID on all policies, only in instances where it is requested.
I have Aetna, for example, and they pay for a lot of stuff, including a lot of my HRT. My blood tests are REALLY expensive, but the hormones themselves are covered pretty well. My therapy visits, too. I don't think Aetna covers SRS or FFS.
My SO works for Wachovia bank right now, and with the merger with Wells Fargo, I might get to switch to an insurance carrier that DOES cover SRS.
The point to my incoherent rambling? Check before you buy. If you're not sure, make a few calls. Just probe around. You don't have to admit to having anything, just ask for a list of all exclusions. Or something like that.
Also, the HRC has a very nice workplace equality book that they publish every year. It contains information about benefits and includes some information on transgender coverage and which companies offer health insurance that includes some form of TG coverage. It's definitely worth checking out.