This video by CBC Marketplace discusses the bylaws that tow truck operators are required to abide by. It's technically illegal for a tow truck driver to show up at your scene without you calling them. They are not allowed to 'prey' on you. They may twist the truth and claim to be working with the police or claim that someone else radioed them in. You do not have to give these tow truck drivers in Etobicoke, Toronto or Mississauga permission to tow your car. You should only allow your car to get towed if you've called a tow truck and by the tow truck company who answered the phone when you called.
Grey County, Ontario OPP suspended the permit of a tow truck driver after purportedly smelling liquor and requiring a breathalyzer test.