The term "kiosk" might not be the best English translation, but "火车售票处" is what we're trying to describe. It matters not if they are hole in the places, as long as they have the ability to sell and issue tickets on official stock. Are they allowed to print tickets purchased on Ctrip? Your PEK experience suggests no, but I'm encouraged by the fact that a random kiosk in Nanning (most certainly a hole in the wall) could.