Look at the screenshot, all the railroads are fully funded, even the one only funded by two capitalists.Some of the railroad construction is waiting for cement. Is that because the capitalists don't have the money to buy it or is there just no supply of it? If the latter: too bad your cappies aren't building factories for it with your coal supplies..
So the answer must be option no 2. No supply (Nations with higher prestige are vacuuming the WM for their own needs).