Due to lag they can't make collisions work in GVs. You could be 100 feet away from a GV on your front end and the other GV would see you slamming into him. As for the "driving a jeep into...." film it, and report it. I believe HTC has deemed it on a par with reporting the locations of CV to the enemy. Poor game play, and it could get you muted or banned.
Happened to me yesterday. No I don't have a film, but buddy in the jeep managed to kill my Panther with his 50 cal.