It's possible I guess, but I don't see why anyone in Boston would have heard of him. Graham is a legendary figure in the Mojave, the NCR, the Legion, and among some of the tribes in the surrounding lands, but while that's a large expanse of territory it still may as well be the opposite end of the world.
Graham is one of the more interesting characters in the Fallout setting, but I don't think he should be referenced in Fallout 4 just for the sake of being referenced. If there's a good reason sure, but I can't think of any good reason as to why we would hear about him in Boston.
It's implied during the Honest Hearts ending slides that, unless he dies, his survival becomes common knowledge at some point since stories of his actions begin to spread to "distant lands". I highly doubt these distant lands include the Commonwealth, though.