Electric power steering works differently that hydraulic. As you turn the steering wheel and the wheels don't you put pressure on a switch. When the pressure is great enough on that switch it turns on the electric motor to assist you. How much force it gives you is based on how much power is sent to the motor. It's all computer controlled. The computer knows the position of the steering wheel, which direction you are turning it, how fast you are going, and the position of the steering box. I would doubt that they would put that much engineering into the system and not add in limit switches to stop putting extra pressure on the steering system when the system was being overloaded (trying to turn your wheels when against a curb, reaching the racks limits, etc). In the future it will most likely be fly by wire and the steering wheel wont be connected to nothing but sensors and a force feedback system like a joystick for a computer game has.