Tans usually have whats called a KILL BOX. which is usually on the hood of the tank. The tank will be shut off. (The kill box is like an engine cut off) So yes anyone can take out a tank. Tanks are usually used for missions in the scenario game.
A scenario game is a long game with a plot. There are different ways to when (taking out forts, capturing special people, finding things, etc.). A lot of the time they are based on movies, wars, and other events. It uses many missions to get your side points.
I've never been to one, this is just what i got from APG. so if anyone has anything else.