I'm not sure if this is exactly what the ranger service is.
Basically over the last year or so Tesla has been gearing up to do a lot more house call type service. It's really the only way they can manage so many vehicles in certain regions.
But, there is a limit in terms of what they can do. It's not like they can do an alignment, but they can take care of quite a few things. As an example I complained about a squeaky seat (it rubbed against center console), and that was an easy thing for them to come out and fix.
More info on tesla rangers. Basically the nomenclature they used for their mobile service fleet.
Tesla updates service operations ahead of Model 3, expands ‘Ranger’ program for mobile repairs at owner’s home or office