Stubbs, what you're referring to is the Yat accent of New Orleans. You're right in that it could similar to a Brooklyn accent but only a small percentage of people in New Orleans have that accent. Marcello in no way had this accent.

I'm slightly confused over what some are considering a southern accent. Of course, these aren't your stereotypical Tidewater accents but that's just one of many. Would you not consider Marcello and Trafficante to have a southern accent? I would argue an accent native to the south would, by definition, be a southern accent, which both have.