Thanks for your research. Most of the examples given are in fact objects relevant to the initial question. Nearly all of them are tagged as landuse=industrial + industrial=depot, a few additionally with “maintenance” added in the name or a separate tag depot=maintenance.
In the earlier quoted topic in the german forum that was one of the options discussed and I’d say this is a reasonable approach. If any of these facilities would be tagged as
landuse=industrial + industrial=depot + depot=maintenance + operator=*
(+probably a name if a “real” name is existing) it should be very much clear which kind of depot is operated at that location.
These are all existing tags so no new tag would have to be introduced. Could that be a solution?
I have to add that a minor problem is the use of the landuse=industrial tag for german users, as has been expressed in some earlier posts. The reason is that the german understanding of “Industrie” is different from the meaning of “industry” - in real life as well as in OSM. The english “industry” covers more or less any kind of productive or profit-making enterprises whereas the german “Industrie” is restricted to “large scale manufacturing enterprises”, comparable the “manufacturing industry” in english (which is only a subset of “industry” in general).
That is why some users claim that a depot or maintenance yard cannot be landuse=industrial because nothing is manufactured there whereas for english speaking users this is perfectly fine, because all kind of warehousing, transport, storage and maintenance business is “industrial” (probably more specific “light industrial”). I’d say this would be well worth to be discussed in a separate topic to clarify the differences and streamline the use of the affected tags.