Train Smart card (Beijing metro)

No, it can not be used in Shanghai, Xian, and Hong Kong.

I used the smart card in only BJ and hong kong. For BJ, there were substantial savings if you took the long distance buses to places like bandaling or mutanyu. For hong kong since the subway cost varies by distance i didn't want to hassle with the machines. For other places in china the savings would be minimal for short term visits