Me too am interested in languages and especially the English one. I am afraid that Eisenbahnmuseum is a bad choice of word in the original text, and I meant that it means preserved livery only in this context.
Otherwise, a common German expression is Museumsdampf, which literally translates into museum steam, but in fact means a working steam locomotive, which may but may not be in a museum. As the Germans have no Tornado the German language does not differ so much between railway museum, heritage railway, preservation railway and so on. We did have Plandampf in the 1990s though.
Translation services often don't get it right when translating English to German. The German language makes no space between nouns when the first one is a nearer description to the second one. Railway means Eisenbahn and museum means Museum, but as a railway museum is not a railway and a museum (as assumed by google translator and the likes) a railway museum translates to Eisenbahnmuseum. The trained German eye at once distinguish the two words as Eisenbahn|museum.
Regards
Felix