Can I use the beijing yikatong outside beijing?

Hi,

I was in BJ couple of days ago and couldn't return my yikatong as I nearly missed my flight. And now I am planning to go to Xi'an for 2 days and was hoping t use the BJ yikatong there as it still has CNY50 in it. But I am not sure whether I can do that or not. Can you please advise. Also can you please give me some suggestions as to which must see attractions should i visit in those 2 days and how! Thank you!