Yes, it is possible. You will want to change the start type of your drive ability to manual and then within the behavior tree use the start/stop ability task. You'll likely want to first move the agent into position near the car.
Okay I finally got the NPC to start the drive ability, but I cannot get it to control the car at all. RCC still wants me to control the car and not hand over the controls to the AI agent even though I have my own character that I’m using without a drive ability attached. So I think the RCC vehicle controller may not be able to have AI UCC agents control them with Behavior Designer if the NPC has to enter the vehicle first. It’s that switch between UCC to RCC that screws things up for an AI.