Just checked out an aerial photo....it's pretty clear theirs is an underground system.

If I board or exit public transport near the driver/operator of the vehicle, I usually say hello and goodbye or thank you. I probably do this universally, in the local language if I know it, even if the operator just thinks I'm an overly-friendly tourist. But it's not something I obsess about or go out of my way to do. If it's a long bus and I'm exiting through a rear door, I don't bother. Driver can't see or hear me anyway.