I could've sworn a local train that navigates a mountain pass had regenerative braking. I appear to be mistaken.
Dynamic Braking (wikipedia link if you prefer) dissipates all of the electricity generated as heat. These trains are clearly referenced as engaging the dynamic braking system during a braking scare in the 90s, and not a regenerative braking system. A 2004 paper obtained dynamic braking data for this train line.
For further evidence, I ran some informal youtube and google searches. There are no videos for "train regenerative braking", but a lot for "train dynamic braking". Google searches only turn up papers for "train regenerative braking", but "train dynamic braking" returns plenty of magazine articles and press releases