As only ~65% of the polish rail network are electrified, I'm sure there are still plenty of Diesel powered trains operating in Poland.

[1]: https://en.wikipedia.org/wiki/Rail_transport_in_Poland

Some more: https://pl.wikipedia.org/wiki/Lista_spalinowych_zespo%C5%82%...

This view was common for me some years ago: https://commons.wikimedia.org/wiki/SM42#/media/File:SM42-838...

I said "diesel" as a mental shortcut for diesel and diesel-electric, but certainly not for electro-diesel.

Already exists. 160 tonnes, swappable batteries, converted old diesel trucks. Australia has figured it out.

Hydrogen is also already used for trains - https://www.alstom.com/solutions/rolling-stock/alstom-coradi...

Guess it would work as a stopgap measure.

Probably because the cost numbers for systems that have never been demonstrated can get away with magical optimism, while existing technologies are constrained by historical data.

Battery trains make sense, they're on order ATM:

https://www.riotinto.com/news/releases/2022/Rio-Tinto-purcha...

https://www.bloomberg.com/news/articles/2023-10-20/challenge...

    Rio Tinto purchased the four 7MWh FLXdrive battery-electric locomotives from Wabtec Corporation with production due to commence in the United States in 2023 ahead of initial trials in the Pilbara in early 2024.

    The locomotives, used to carry ore from the company’s mines to its ports, will be recharged at purpose-built charging stations at the port or mine. They will also be capable of generating additional energy while in transit through a regenerative braking system which takes energy from the train and uses it to recharge the onboard batteries.

It prevents double stacking rail cars

Here in Germany on some tracks some trains also run on battery. As a test case we had such a train for some month to replace a diesel train. They just had to return the test train.