In WW1 rail was generally a disaster - the problem for the Russians, as I understand it, wasn't that they had insufficient food - it was that it wasn't getting delivered to the cities - the peasants hoarded it, production was down, but not by THAT much, and the rail system collapsed - diversion of the transport necessary to support the military was the main cause.
I think GoA has a very subtle and clever system
BTW I'm pretty sure Turkey did not produce a surplus of raw materials in WW1 - in 1914 the Ottomans produced 826,000 tons of coals (another source says 651,000) - vs 40 million for France, and over 200 million for each of UK & Germany.
when the Russian navy lowered sea-borne delivries of coal from the north coast of Anatolia there was no rail to use as a standby, and Germany had to deliver some 12,000 tons of coal/month to Istanbul to make up the shortage - the balance isn't quite right in that area as there's no real naval war in the Black Sea. (as an aside 1 book says that the coastal shippers opposed making a rail link that would have helped with the argument that it would be redundant when peace arrived, and they didn't use Goeben to escort colliers because each sortie would use as much coal as the small fleet could carry!)
by 1 October 1916 the Germans reckoned they had sent 600 million Marks worth of goods to Turkey, but received only 50 million in return.
Before the defeat of Serbia some goods passed along single track rail lines in Bulgaria & Romania, and included a section of passage along the Danube, and the Romanians actually sopped co-operating shortly after Turkey entered the war - October 1914 I think - and only a handful of wagons made it through before then.
It is quite interesting trying to come to grips with the differences in economics and industry that existed 100 years ago - I got a couple of books written in the 1920's about the Russian economy and the British blockade - both delve much into exchange rates, trade deficits, the raising of money via taxes and war loans, etc., and the consquences on what were essentially free market capitalist economies - at least insofar as there seems to have been few if any attempts to force private resources into government directed activities. There were certainly restrictions on who could get resources, but all manufacturing was still "for profit", and of course there was much made about war profiteers.
It was a completely different time and set of attitudes.