What if you jam the railroad communication on accident? Do you know what frequencies the engineer, conductors and operations center is using?

Well first of all, if their service critically depends on wireless communication, then that's bad design.

Further, I imagine you turn up the amount of power of the jammer until the person on the phone gets bad reception.

I don’t know what you mean by critically. But everything from calling law enforcement for pedestrian and vehicle strikes to handling special operations (i.e. single tracking in a work zone) uses wireless communication.

There are also defect detection systems that rely on radio transmissions to indicate if a train is for example dragging equipment.

And if someone in the next train carriage dies because they're having a heart attack and no-one can call for help (including the driver/conductor), you'd be liable for manslaughter.

Loud conversations in a public place are annoying, but guess what? it's a public space, and you don't have a right to quiet there, let alone exclusive control over radio communications. The sheer entitlement in your post is astounding.

I’ve heard of this psychological problem some people have: where they are disturbed by nearby people talking on the phone. Is there a name for it?

The trouble is that half the conversation is missing, involuntarily increasing the attention of bystanders. Lauren Emberson called that 'halfalog'. https://journals.sagepub.com/doi/abs/10.1177/095679761038212...

Some people just want to commute in silence without listening to overly loud work-related calls made by other people.

I’m one of those people, myself. But then I remember that public transportation means that there might be other people around, and we’re not at a concert where people are not allowed to talk, and that I can’t always get what I want, to paraphrase the Rolling Stones.