The Insurance Bureau of Canada has a confidential Tip Line which you can call to report Uber drivers in Toronto.
If you see a car you know to be or believe to be an Uber car, call 1 877 422 8477 and provide the car's license number to IBC. The driver of that private car can face cancellation of their insurance policy by their insurance carrier.
You are not required to leave your name or contact information.
Insurance Bureau of Canada confidential tip line:
1 877 422 8477