> it has an electric drive motor with a supply pulsing and
> switching up to a hundred amps hundreds of times a second.
I thought the Prius had induction drive? If you're going to get an interference from anything, it would be RFI from all the onboard electronics. Since this vehicle has to undergo all of the EMI/RFI and susceptibility tests any other car has to go through, I wouldn't treat it differently than any other car. Carefully pick your power/control head/antenna cable routing, ground and bond everything well. Might be interesting to use a sniffer loop around the car to find the "hot spots", there's lots more of them in my XYL's gasoline car than my 90kW drive EV. Being electric doesn't necessarily mean more RFI.