I highly doubt that the N900 will work with TD-SCDMA based 3G services. It is a fundamentally different technology from W-CDMA...one is time-division and one is frequency-division. Maybe compatibility is an "undocumented feature", but I wouldn't hold my breath. Most major Chinese providers will likely be moving towards deploying W-CDMA in the relatively near future according to this:
http://www.umts-forum.org/content/view/1401/303/