I suspect the equivalent of squatters rights apply - since nobody has contested the current use of the land for the last two years that use (parking) may be protected. (If I don’t actively keep people from hunting on my land for a couple of years they get the right to continue hunting on it, and that right even extends if I sell the land, though only to those hunters who can show they have been ‘continuously and uncontestedly hunting it.)
In CA to get squater’s rights the squatters have to pay the property taxes on the land.
You’re right, it’s called a “constructive easement!” I worked for a company in Palo Alto, CA where people routinely drove through our parking lot as a shortcut. The company finally posted security personnel several days a month and turned people around. It was an attempt to regain control over the constructive easement that they had tacitly allowed to be created.