Can a car dealership get a repossession company and a constable to repossess your vehicle?

YES, its called 'writ of replevin" and takes days, not months.

If the repo-man has the proper documents he/she may take it lawfully WITHOUT POLICE PRESENT. The police usually only attend for a "Keep the Peace" call if the repo-man suspects trouble. The police are usually notified of such a seizure because most people reort the vehicle stolen when they return and find it missing.

They repo vehicles all the time. However you could take them to court, becouse it is a denial of "due Process".