Keep in mind that trains expend a lot of their output power only during takeoff. Maintaining a constant velocity requires relatively little power, and with regenerative braking some energy may be recovered (the primary reason for the Li-Ion cells between the power source and the motor).

I don't have any numbers on this, high-power electronics was never my field. But I wouldn't at all be surprised if cruising power was less than 10% of max engine power.