AFAIK, there is no official BB existence in China. In order to get BES access, they have to use BB purchased from abroad (mostly Hong Kong) and roam all the time. The fee for data roaming isn't too bad, at least in a corp view. However, voice charge adds up very quick. At $1-3/min, a user can easily get a several thousand doller bill each month.
Read a news somewhere that China Mobile has/will launch native BB service in China, but haven't really look into it.