But it's really doubtful they can prevent bitcoin from transfering money out of China altogether (unless they ban bitcoin)
No bitcoin and ICO's are a mechanism to get money out of China. Shady HK pawn shops, "family" vacations with strangers (the limit on money moved is per person) and straight up smuggling in bodily crevices are still far more popular. Right now China makes more on bitcoin than it loses because 70% of mining happens in China. So long as this remains true China will not ban bitcoin. Everything else is just noise and FUD.
So use RMB to purchase electricity for mining bitcoin, convert mined bitcoin to currency outside of China (or sell for RMB to someone that wants to do that and use RMB to buy electricity to mine more bitcoin).
China does have cheaper electricity than the west, especially since most of it still comes from cheap dirty coal.
"Exchanges", though, are iffy. Those are financial institutions, and the PBOC can regulate them if they want. They've done a little regulation, clamping down on margin and accepting credit cards to buy Bitcoin.
Bitcoin used to be down in the noise as a way to get money out of China, and was tolerated in the way that putting all your relatives on the train to Hong Kong loaded up with 20,000 RMB each is tolerated. The numbers for Bitcoin are getting bigger, though, making PBOC action more likely.
A few years ago, it looked like yuan convertibility was on the horizon, but that didn't happen.