I was playing a large map (Riverlands). It is map that enforces long transportation, as the landmass is divided by rivers that allow crossing only at some few places. I had smelting works all over the map on almost every island with mountains.
When I explored a new island I built a warehouse, 2 smelting works, one iron-ore and one coal mine. I expected the system to use the new facilities at hand and produce iron and then carry the iron away to ironworks, axe factories, warmill etc. -- but it did not. Instead the mining resources were carried straight from the mines, not even using my new warehouse, and seemingly evenly distributed to every smelter on the map (all idle then).
Is this as designed? I dont think it is an effective system. It generates a lot of needless traffic. I would rather see the system using local facilities first, and only distribute things when their capacity is exhausted.