From: Houston, TX - USA
Urumuchi is about 35 hexes by major road to the nearest general link to a rail line in China...Keisui (92.35). that is a long supply line, and easy to interdict. The supply distance rules, while difficult to caluclate manually, as I understand them would make Urumuchi an unlikely source of general booty. The longer the cacluated LOS / LOB, the less can be moved. If I hazarded a guess, I would suggest your enemy has interdicted or is periodically interdicting that supply line OR you have other bases that are providing from a shorter supply / booty line, assuming you are seeing nothing move out.
A follow on question would be where do you want the booty to go. Even without interdiction, IME, the allocation algorithem may not pull it from there and push it to eastern China. While it is a basic if dirty equation to walk supply along bases to a destination, I have not had success moving booty that way from that base.
Perhaps there are tricks others could share.