What type of surveillance camera are on City buses and subways?

I live in a small town and our city buses have these dark round black bulbs on the ceiling of the bus. What type of cameras are used. Are these surveillance cameras monitored live, and if so by whom. I think the public has a right to know about these things. Generally, I assume its the same in all cities.
How much money is spent to maintain these devices on public transit vehicles. What are the privacy concerns (even thou video recording in public is competly legal?
No debates please I'm looking for factual information.