That's actually quite difficult for this suggestion. The amount of Volts on these lines differ greatly across countries. In this case the intention is to connect multiple countries. In enough countries the tracks aren't electrified. A train which can handle the differences across countries is pretty unique. Tracks can differ in size and lots of trains only handle one electrical system.
See e.g. https://en.wikipedia.org/wiki/Rail_transport_in_Europe#/medi...
I've seen a few "solutions" to dump all containers from Asia in e.g. Spain. This so to "reduce" the backlog. Then have "trains" move the containers to the right place. Aside from loads of other reasons why this wouldn't work, just see how many electrical systems are in use. Aside from just: where are these magical ready to use trains? ;)