I think that would be hard for them considering how advanced technology is today and how secure Bitcoin is. For instance, a friend of mine who recently flew to China was able to access and post to Facebook (he used VPN) without any problems. So I guess a total ban would be really difficult.
But knowing how strict the Chinese government is, and God knows what could happen to you (especially if you're a foreigner) thrown into prison there, then I probably won't even consider mining should it be banned. LOL.