The Observation Deck

Does the city actually enforce the snow parking ban? My street is always filled with people who park there ... and no matter how much the snow, they still park there, even when the plows have a difficult time coming down the street. If the parking ban is in place, wouldn't they (or shouldn't they) be ticketed? Or does it not apply to people whose cars are already parked on the street? Or does it only apply to main roads and not side streets?