This isn't limited to NYC, but I am not a fan of the plasitic sidewalk pedestrian mats found at some street corners. Most are missing tiles and I just avoid them in pretty much any weather. They are NOT safe to walk on with leather soled shoes, or even my duck or comando soled boots for that matter. The plastic provides zero grip and the angles at which they're applied makes it worse.
Similar to this, what looks to be subway, but tiled pieces rather than a single mat.