Nice shots, be aware of the misinformed NY Transit and NYPD. Several photographers have been detained and even arrested for taking photos in the subway system. They always site some "law" that prohibits such photos from being taken. Ironically, there is no such law. In one case the press photographer was arrested and detained for taking photos for a photo contest that the railroad actually advertised.
In all cases, the photographers sued and were quickly awarded up to $50,000. Last Friday I was in NYC, took some photos in the subway, but was not lucky enough to get arrested - no even challenged!
Two links above if you care to read the full details.