Hydrogen probably has some niche uses but there are some things that proponents like to gloss over.

1. It’s not green since most of it is produced from fossil fuels. It’s also disgustingly expensive even compared to fossil fuels. I’d note that the company Orlen Koltrans which is funding this train is a subsidiary of an oil company PKN Orlen so yeah.
2. Even if it were green (e.g. water electrolysis from renewables) it takes something like 3-4x the energy to produce, store, transport, and convert back to energy as just charging a battery.
3. Regardless of how it’s made hydrogen also contributes to global warming - if any hydrogen leaks or escapes during fueling or venting, it promotes the methane production in the atmosphere.
4. It can and does go kaboom. e.g. this hydrogen powered bus has seen better days.

All said and done, I think it’s crazy to even bother with the tech unless its so niche it cannot be done some other way. Japanese automakers & oil companies looking to do a bit of greenwashing have been the major proponents of hydrogen and that should say something. Also the fact that hydrogen has been a miserable failure in areas where it has been piloted.

In the case of trains it seems more sensible to manufacture biodiesel or synthetic fuels than this. It’s certainly safer to transport and store. Perhaps existing trains can be converted relatively easily. Or electrify the train line or stretches of it. Batteries would be an option too - a train might simply hook up to a fresh battery tender and off it goes. Or some kind of hybrid solution that can source power from overhead lines and/or diesel and/or battery. Or even put solar on carriages to reduce fuel consumption during daylight operations. All these things seem more viable than hydrogen.