I'm not sure but the other buildings do look a lot like NYC ... haven't been able to find a photo from that exact angle to verify it though. There isn't a bridge in that location however.
The photo is clearly a composite, even if it's not NYC. I'm not sure that the exact city would matter from their point of view as long as the jihadi banners and the WTC were clearly visible.
It looks like NYC to me. The picure is taken from the other side of the East River, probably about opposite the U.N building looking towards the lower part of Manhattan from the East. The bridge is the Brooklyn Bridge and you can see the waterfront buildings of Brooklyn to the left of the picture.