Today, it's the law.

Whenever an emergency vehicle has it's lights flashing and is parked at the side of the road, you must move over or face stiff penalties.
 
The Move Over Law was many years in the making and finally pushed through after an avoidable tragedy.

"The death of a police officer from Bromont in late December 2011." He was hit by a car as he stood on the driver's side of a vehicle he had just pulled over.
 
Transport Quebec's Mario St. Pierre details the move over law.

"People have to slow down, and move on their left to create a buffer zone between the stopped cars, either on the shoulder or a lane."
 
The penalty if you don't move over is $200 to $300 dollars AND 4 demerit points. 

And don't even think about ignoring the law in Ontario.  Fines start at $400 and can go as high as $2,000.