Much of the Trans-Siberian is electrified.  Between Beijing and the Mongolian border you'll pass a number of coal fired generation plants...they sit right along side the tracks (in fairly remote areas). I'm guessing, those supply power for the train and cities. At the border, engines and wheels (different track gauge) on the entire train are swapped...after which you'll begin noticing the smell of diesel exhaust.

However, this IS, hands-down our best bet for clean & abundant power:

 https://youtu.be/bDw3ET3zqxk