Arena Wars vehicles nerfed for missions (XBone)...

So - I bought and fully upgraded the disco laser deathbike thing. so far, it's killed me more times than the Twatbike - usually from boosting my head into traffic lights.

I took it into some contact missions and the primary weapons do not affect target vehicles. Normal vehicles in traffic respond to the "lasers" as they would under normal 50 cal fire. For the target vehicles however (Trash Talk trucks, Blow Up cars and such), all damage is cosmetic. My friend tried guns from another Arena Wars vehicle, with the same result - the vehicle weapons do no damage.

Am I doing something wrong, or are the Arena Wars vehicles only useful in the Arena?