Whew! That was a hot story, N13! I really love being adventurous in public places and I'm a bit of an exhibitionist, so I totally dig the idea of pushing boundaries if I see/feel it is welcomed. You kinda get a good sense for those things...kinda like a gaydar. For some reason my hottest train stories seem to be centered more in the euro rail than in the US subways/trains.
Unfortunately, these days folks are so wrapped up into their cells and headphones in subways, airports, etc, that we don't give each other the chance to connect, much less play with each other. I've been trying to become less tethered and more aware of my surroundings to capitalize on human connection and stimulation of all sorts.