There are flowers in the passsengers compartment too. The bus is a civilian version (panoramic roof). The photos obviously were taken before the outbrake of war, there was not yet large requisitioning of cars/busses. Thus likely it is still civil registered, as those trucks and that motorbike on the road.
In war time such busses were requisitioned complete with their owners/drivers. (At least I know one such case.)
Those trucks and that bike however are all civil registered in the far North of Germany. Maybe they had been leased there and taken with the unit which was regular stationed in the North. The bike at least is a civil version too. They got an army marking (WH) that otherwise would form part of the licence number.
However requisitioning started already in spring of 1938. So these vehicles may already be requisitioned at that early stage, but still kept in their civil state and their civil licensing, only added with that painted army marking.
Anyway, it is the first time I see vehicles obviously in regular use (army marking) that are civil registered.
Military licence plates go back to 1923.
EDIT: I got one photograph of that requisitioned bus and owner/driver, where the busses already had military varnish and tactical signs but still civil registration, and the driver still wearing his pre-war tenue...