If there is an open beer in a car, you can't prove the driver was drinking.
If there is a call or text using the drivers phone from within the car, you can't prove the driver did it.
If there is any phone activity within the car, you can't prove the driver did it.
Phone use in cars causes accidents, and the solution is to remove the cars from the possession of drivers who endanger everyone else.
Having to listen to someone else on the phone is still a distraction to the driver, so it really doesn't matter if the owner or someone else is using the phone. Numerous studies show that half conversations take attention away from people who can hear them, thus, by allowing this to take place in a vehicle you control is putting others at risk. I don't think it matters who is using the phone, if a phone is in use in your car, and you crash, you should lose your car.
Besides :
1) Most cars are single occupant these days during the commute hours when most accidents happen, so it won't even be an excuse for most people.
2) Most passengers are either kids, who aren't calling or texting your contacts on your phone. Again,
3) Most other passengers are adults with their own phones.
People can drive without a license. Take the vehicle.