I was in a big team game last night and was (in effect) betrayed twice (shame on me then).
It went like this:
Other player gets in drivers seat and waits for teammate to get in vehicle
Once teammate is in, the driver puts vehicle over cliff but exits just beforehand.
This is, in effect, a betrayal. The one causing the death gets no penalty.
However, if the aggrieved player mellees the traitor he is booted for betrayal (ooh, shame on me agian)
Code of conduct probably has some section about naming other playes ....but hey, I'm trying to help everyone here.
I didn't get the name, but the tag is ZOMG or something similar. Just never get in a vehicle with that one.