Keeping a battery or even a cab warm doesn’t require so much electricity. Also, it depends on how the electricity is generated (hydro, nuclear, coal with much better scrubbers than a small ICE). Even let’s say the electricity is generated by coal without decent scrubbers (something not allowed in the USA at least, but let’s pretend we are in Mongolia): the coal plant is still way outside of the city (in this case, Ulan Bator).

I assume the vehicles are idling to keep the heater on, or the engine warm. Also, it seems like diesel is different from unleaded gasoline in terms of what engines can do or not.