While T-Mobile continues to upgrade their existing infrastructure to include 4G LTE, that isn't keeping them from pushing forward with more advanced technologies in other areas as well. They just started rolling out what they call their "Wideband-LTE" in New York City.
The new upgrade will effect areas in Manhattan, the Bronx, Brooklyn, Queens, Staten Island, Long Island, and Northern NJ. It basically includes data speeds up to 100Mbps. You can see the full press release in the thread below.
Source: T-Mobile Wideband LTE Blows by the Competition in New York T-Mobile Newsroom