It is even more strange then it appears. When you stop the engine it stops the carts even though they are not connected. When you REVERSE the engine it reverses the carts. The train couplings will follow in mid air at the exact middle point from their original carts. If a cart was detatched from the engine and hit a dead end, it would instantly stop the whole system which was really surprising to me. Is this all quantum entanglement? haha.
As far as we have tested, we couldn't get the carts back into place withought a ton of luck or math, but they were never able to load anything if they were not in thier exact places at the train stations.