Currently, on Chinese Tango devices, there is a Games tile that links to the games category in the Marketplace. All an owner needs to do is use a Windows Live ID from outside mainland China, and the Game tile will change to the Xbox Live tile. Windows Live IDs from Hong Kong will work as well.
This workaround does not restore any Facebook or Twitter functionality, but with WeiBo and RenRen being the preferred local alternatives, that is probably not an issue for most.