Crap, they might JOIN WITH THEM.
Nah, the Mafia is still traditional. They won't join with non-Sicilians and seldom associate with non-Italians. They only work with the Jews...or as the late Meyer Lansky once said...the "Kosher" Nostra.
I grew up in Cleveland, and they could have teamed up with the Irish there and made a killing. Instead they blew up Danny Green in his new Buick.........
Big Al HATED the Irish and Polish gangs in Chicago, too. Look what he did to O'Bannion, Weiss, and Moran.