Sounds like the old "Hospital on Wheels," "Specialized Cardiac Care Unit," and "Dedicated neo-natal Ambulance." They were usually 1970s gas guzzlers sporting the "Latest Lifesaving Equipment" a physician, nurse, driver, etc. all packed into a rig the size of a motorhome, and shortly fizzled because they were personnel intensive and could never run enough calls to keep a specialty unit such as this in service. The MD on wheels is kind of a retro-idea going back to NYC-EMS horse-drawn rigs running out of Bellevue having an ambulance physician, usually an intern, handle the role- later delegated to a first-aid trained "attendant" in most later ambulance services.