[yokohama11]

The abandonment side doesn't really make a whole lot of sense.

There's plenty of train lines in the US that are kept on the books/maintained, yet don't see any regular service. Some brush cutting, an inspection train once a year, and that's about it.

There's also plenty which are entirely abandoned and overgrown in practice, yet are still kept on the books, which means the train company retains the right of way and can resume service at any time it wants even though a train hasn't run on it in at all in 30 years and it currently looks like a forest.

Training for emergency detours makes some sense, although unless the line is long you don't really need all that many people trained to be prepared for that. You can have a few people qualified and they can just get on/off the train (riding back and forth) in the section the normal engineers aren't qualified for. And if it's once a decade or longer planned work, it's going to be cheaper to qualify the workforce right before it rather than have to keep them all up to date all the time. (I'm also sure that not all of these lines are worthwhile detours)