My question is, then: as it seems everyone studying "Chinese" as a second language learns Standard Mandarin, does it actually function as a proper lingua franca in (mainland) China? This guy is quite an important figure and so I'd doubt that he would make a socially-risky move like that, so he either knew they'd understand or was just ignorant after all. I mean, for example, obviously Cantonese is the main player in Hong Kong and such, but to me at least, automatically speaking (Standard) Mandarin to someone from (mainland) China seems like automatically speaking German to someone from Swizterland-- and if you've ever been to popular, picturesquely-Swiss places like Lausanne or Geneva, you'll notice that that's not always so clever to do... yet we (usually) automatically speak English to Canadians.
So what's the deal here? Would it really be entering a closer sociolinguistic sphere by using (Standard) Mandarin over English with, say, Hakka-speaking Chinese-- or would English and Mandarin have roughly-equal status in this situation?