The rail network in Germany is in so bad shape that they had to get a centenarian out of retirement. That is, a steam engine built in 1921 and retired in 1977.
But let's start at the beginning.
The rail network runs on electricity.
Sometimes when there's big time repairs being done, there can't be electricity around that spot.
To transport materials to a railway construction site without electricity, you need an engine that doesn't run on electricity, but carries its own fuel.
So you get one of the remaining diesel engines.
Unfortunately those are getting rare, and there are a lot of construction sites, so at one point a company doing construction took to contacting an organisation that keeps historic trains going for train lovers as sort of museums, and asked if they could borrow their diesel engine.
The diesel engine was not available, but the museum guys joked that they could offer a steam engine. And the construction company was so desperate they accepted.
That job went well, and people in the business were like "hey, the old girl still got it!" so the steam engine got rented for more jobs like that.
At least one time a fire brigade had to help out with upping the water supply, I guess becaue not every station is equipped to do that any more, but over all, well. She occasionally pulls freight trains instead of passenger trains full of fans of historic trains.
Sounce links - mind the article is German:
original source: https://bnn.de/karlsruhe/ettlingen/kurios-dampflok-58-311-aus-ettlingen-zieht-wieder-regulaere-gueterzuege
archive link: https://archive.ph/pQFrj#selection-739.22-739.28
