Yes they use solenoids.
I thought of this but it won’t work.
You have two wires to the solenoid. Call them a and b. At rest both are connected to ground. Go to lock the car wire a is energized for a moment and since b is grounded the solenoid energizes and pulls the lock to the locked position. Go to unlock b gets energized, a is grounded so the solenoid magnetic field is reversed and the lock is pushed to the unlock position.
Here are the problems with your theory
- How do induce voltage in just one wire, not both? They are side by side in the harness. Voltage in both wires = no current flow.
- How do you get the voltage in the unlock wire and not in the lock wire?