Massachusetts law indeed says that "ownership" in the tree (as a "wood resource," etc.) goes with the location of the bole. BUT Massachusetts law says a lot more "nuanced" things about branches, and cutting branches, and about trees that are obviously significantly diseased, and about trees that are healthy. Long and short, if the tree is in good shape, your neighbor can be required, by reasonable "arborist standards" to maintain it (including reasonably removing dead branches before they fall on your lawn). You don't have the right to remove branches at will unless you can show "legal nuisance."