I think the Q&A already confirmed they weren't adding coal. We already have oil derived fuel in the game, and in my opinion it wouldn't make sense to add coal for just trains.
No but it would make sense for raw material production. Availability of coal was directly applied to how much steel you could make which then effected everything else you could make. Even for the Luftwaffe the largest raw material was steel for all the bombs, bullets, shells, and rockets they needed.
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