We have been location scouting in Turpan and nearby areas recently and it is indeed difficult to shoot in Gaochang at this time, not just because it is Xinjiang but it is a heavily Uiger area and one of the centers of the recent unrest. Gingerfilms has local producers in Xinjiang and good relations with The Xinjiang Film Studio, which handled the locations and permissions for such recent movies as The Kite Runner, we can coordinate permissions for your shoot through them.
As my comrades above have pointed out it does matter quite a bit what you want to shoot: purely scenic shots of the ancient Gaochang city, the Karez irrigation system and incredible surrounding Turpan basin would not be difficult, interviews with local people about their thoughts, opinions and daily life would be almost impossible even with your handy public security bureau deputy on hand to guide the interviewees answers. Other areas of Xinjiang are quite a bit easier to shoot in at this time even other Muslem areas as long as they are not Uiger, for example the Kazek areas in the North-east and Mongolian areas which run a north-south line through central Xinjiang. If you can share more details on your project gingerfilms would be happy to help you put your production together. You can reach me on shane@gingerfilms.tv, skype: billy-shane-nunn or call 861 381 861 9991