Some German fire services use white vehicles, to which red or red and yellow reflective tape panels and/or stripes are added, instead of multi tone paint finishes. This could be such a vehicle on a shakedown drive or perhaps a demonstration unit, as it is on temporary license plates. A third option is that it could be an export model, as there are a few fire brigades in different countries that have all white vehicles...
Ed: in former times there were white brigades in Britain such as Grampian, West Riding etc. See
Added by on 09 November 2021.
There are several in the US too, although none of them would be very likely potential customers for a European specification ladder tower on a Mercedes Econic chassis! A few cities in Texas and Florida have white vehicles, but most belong to volunteers in the North East and Mid Atlantic, reflecting traditional liveries going back 100 years or more. There are also quite a few blue, green and even black liveries amongst these volunteer outfits, although of course good old bright red prevails...
We in Tayside had a white Dennis F24/Dennis/TFB FO/ST before Grampian. A 1958 reg No HTS163. Originally red and a pump before being converted. It had a 9-10 metre ladder on the offside with a large fan on the rear above the pump. It served at the Kingsway from 1972 - 1976 before disposal. My father has driven it.
Ed: in former times there were white brigades in Britain such as Grampian, West Riding etc. See
Added by on 09 November 2021.