I don't even know what that means. And it is not a "well established doctrine". Certainly a person has a privacy interest in a vehicle to be free from unreasonable search and seizure from agents of the state. The right is much less than with a home as demonstrated by the legalilty of a "Terry" stop and search. But any employer would have the right to require consent to search as a condition of using a parking lot. The employee can refuse and work, or park, somewhere else if that is his desire.
Can an employer require an employee to wave OSHA regs as a condition of employment?
And what the hell is a “terry” stop?