It’s certainly not all you’ve ever been able to do. The express train from Chongqing – Beijing and Chengdu – Beijing was running from January 11th 2011 until some time later that year. I took it on 20th August, it worked, it was fast, although they obviously found it wasn’t very safe so cancelled it. In that way, you can say I am lucky to be here!
It was direct, not via Xi’an. It stopped 4-6 times, but I can’t remember where. I will try to dig out some photos if you need more proof!
The Opening:
The Closing:
http://www.chinatraveladvice.com/forum/112/974-fast-trains-beijing-chengduchongqing