How do the streetcars in Toronto draw power from the lines?
Power feeds in from the overhead wire and connects to a pantograph pick-up on the roof. This routes the power through to a controller and then to the motor and the return path for current travels along the rails: -



I used to remember a thing called a trolley bus in my home town when I was a kid - it was a regular bus with rubber wheels but had a double overhead cable pick-up - positive (it was a dc feed) was on one wire and negative (return) on the other. Ye olde trolley bus: -