Ok, after looking at you sidings in the center and the timesaver area it appears each pair would a be customer. The miner, logger, producer is in the yard already.
One cuts and builds a train in the yard, delivers in the proper order by dropping off the "fulls" and then collecting the "empties" on the other siding, proceeds and returns to the yard to the A/D track, where a switcher moves the cars around.
They magically get full and the customer empties theirs.
If a structure that you have is a producer, it doesn't matter. You take them empties from the yard and bring fulls back to get sent to some imaginary location.
The structures define the story, the action is the same - drop and pick at every location.
