the Sicilians are no longer the predominant OC group in Canada, nor is the Montreal Mafia for that matter. Its arguably the 'Ndrangheta, however that doesn't mean Costa was saying that the 'Ndrangheta control Montreal.
Think this is a pretty accurate summation.
MORGAN: Why didn't you fight him at the park if you wanted to? I'm not goin' now, I'm eatin' my snack. CHUCKIE: Morgan, Let's go. MORGAN: I'm serious Chuckie, I ain't goin'. WILL: So don't go.