@Cattledog
The IR drop along the power cable between the locomotive and each freight car's power connection would be very high without high voltage conversion enroute. However, each freight car could be self-propelled. 4 locomotives at 4600 HP each can pull roughly 30 or so loaded ordinary freight cars over the Sierras, so moving the motors to the cars would need only a few hundred HP each, spread over electric motors on 4 axles (order of magnitude estimate). The tractive effort (and regen action) in each car could be controlled by a small locomotive at the head end by radio to control car-to-car slack action.
Of course, these batteries would be technically in "used" condition upon arrival. Intriguing concept.
Oliver