Respectfully, I think you are inventing a problem that wouldn't exist for the city. Land parcels are defined by area and not by parking spaces. You can refer to your local land survey for reference.
Perhaps you are thinking of Torontonians with "parking pads", however they are leasing part of the public boulevard from the city for iirc $296/year, so the city would simply no longer charge these people.
Parking spots in condos are also treated as land parcels. Regardless, I do not think these people would have a claim against the city as there would be no reduction in their land area nor easement/expropriation required on the city's part to convert a public boulevard.
Source for this take? I lived in Sydney for years and never noticed any kind of dramatic discrepancy in property rights there, again not that they would "owe" anyone for their land that they happened to be using for parking anyway.