Nothing obvious in FindLaw for Massachusetts. Most "Gun Free School Zone" references are to use of the Interstate Commerce bit - nobody had a gun near/in a school.
Unless the opinion included "oh, yeah, that's come up before, never made it to trial, so there's no precedent, but there shouldn't be an issue", it's not clear what a legal opinion offers.
Here's a question: are there known events where Boston police discovered persons with valid LTC-A (All Purposes) carrying, by some circumstance not in itself warranting arrest, and then arrested the persons? For instance, they stopped the wrong guy, found he was carrying, had a valid license, but arrested the guy and seized the gun anyway, and the guy had to hire a lawyer to get things cleared up.
That is, if "caught" by police practicing fully legal CCW, do you usually need a lawyer to get off the hook and get your gun back?
I don't know if there is any public knoledge of such incidents by forum members.
My idea is that if one usually needs to hire a lawyer when "caught" not breaking any laws, as Boston is a PITA on gun issues, then I'd know the risks are essentailly equivalent or worse for my issue.