Turns out, it's some form of electrified A-Class. With yellow hybrid sticks affixed to the front and rear windscreens, a yellow warning cone on the rear seat, and filler caps on both rear quarter panels, it seems very likely this car is a plug-in hybrid prototype.
It should be noted, the photographer who took this set of photos couldn't find an exhaust tip at the back of the car.
With so much camouflage on the car, it's hard to tell what styling changes, if any, Mercedes-Benz will employ to differentiate the PHEV variant from its conventionally-powered siblings.
The fourth-generation A-Class seems to be very close to take off, with the company not only running almost naked prototypes on public roads, but also revealing its interior design.
Given the level of camouflage on this electrified model, we expect it to make its debut a few months after its internal combustion-powered counterparts.