Angel Thorfinn:
Maybe I stand to be corrected, but I don't think the issue here is if there is a road or no road connecting the two SYs. If one SY is on "Getting Goods", and the other is on "Accepting Goods" the cart pusher from the "Getting Goods" SY will attempt to travel accross country to get goods from the other SY - road or no road. As you indicated, the pusher will still need manned ferries.
It seems that the issue is why are goods from two SYs in "Getting Goods" mode being exchanged.
I have seen this occur, but it is usually right after I change a SY from "Accepting" to "Getting", and the cart pusher was already on his trip to the Accepting SY before the change was made. After the first trip the problem corrects itself.
But it sounds like Gil Britannica has been experience this problem over a long period of time.
Would really be interested in what you find out.
Regards,
Vriesea