Being that New York (especially NYC) contains big business, they are going to have a very high percentage of BB users, and this is likely what helps makes Blackberry the most used in NY. While some businesses are moving away from Blackberry, the main reason that they have stayed legitimate is business users.

Although, that might be changing over time. At the same time, whenever I've been in NYC in the past few years, I mostly have seen iPhones, but the 2nd most phone would be BlackBerry. But I assume, if I were closer to Wall Street or another business district, I would see more Blackberry users.