Tanks Sitting on top of Mountain in North base on Firestorm Map

If tanks want to sit on top of a mountain, they'd at most harm their own team and cause a minor inconvenience to the enemy team. You can't really do anything about them, but they can't really do anything about you either. 

It's stupid, but it doesn't warrant any action. The best action to take is to just use your own tanks to pressure the objectives.