Similar thing happens in Australia: https://www.jalopnik.com/these-electric-trains-never-need-re...

The twist: these trains aren't connected to the grid. They use regenerative braking to charge batteries when carting ore to the coast, and the batteries power the trip back to the mine.

IIRC there are mine trucks set up similarly in some locations, they're loaded at the top, regen downhill, and that's sufficient to power them back up the hill when empty.