I googled and found this (
http://thinkprogress.org/lgbt/2014/06/20/3451591/massachusetts-transgender-health/). If that is the latest, it does certainly seem to indicate that the Division of Insurance says that medically necessary treatments, including surgeries, need to be covered.
It is described as "guidance," however, so I suspect that this is not a binding decision the way a court finding would be. This is, I believe, the executive branch defining how it is going to interpret and enforce the law. It could conceivably be the insurer's plan to press its luck and hope nobody notices this. However, that's just my non-lawyer guess at what might be going on.
It might be more plausible that the person you talked to was clueless. Can you obtain the official list of exclusions? (I don't know what it's called.)