no way they would have the balls to try and mess with ny, and i also can't see why would they want to hit bellomo or cefulo but to the answer you question, then no they are not that strong to hit a gambino or genovese boss and get away with that.
and as far as i know they were strong in canda and had a lot of associates and political connections.
but let's wait to some guys like scalish and hollander and more guys here who knows better in canada to see what they think