Unless you're in a sufficiently carbon dense region (third world maybe) it seems exceptionally optimistic to assume the train will be able to power more than it

Unless you're in a sufficiently carbon dense region (third world maybe) it seems exceptionally optimistic to assume the train will be able to power more than itself in either scenario. Not that it's not a good idea anyway but unless the train can cover itself with spare change leftover you're not going to be powering anything extra without creating waste.