Isn't part of the definition that 2 cars counter-balance each other?
Typically elevators use their own counterweight, not other cars, as that would be less flexible for traffic. Since the counterweight can fit in the same shaft space beside the elevator (the shaft is designed with a little extra room for the weight), this eliminates needing another elevator car.
Most places I've been in with elevators have only one car/shaft - only very tall buildings have multiple elevators beside each other.
I recently got stuck in an elevator ". It was at the top floor of a parking structure so no one could hear me yelling. Damn thing didn't respond to any of the button presses. Even the emergency call was busted. Thankfully as I was about to call the police someone from the outside called the elevator to a floor below which worked. Needless to say I told them NOT to get on lol