There's no reason why they wouldn't be allowed to use a government-backed cryptocurrency, given that the reason they're opposed in the first place, is that they cannot be controlled. If China comes up with some kind of digital money, you just know it's going to be heavily used in surveillance and is going to be heavily controlled. They might prefer that WeChat users (or all their citizens, really) use such a currency, even, because that's only going to make things easier for them.

China has gone so deep in surveillance, that the moment they introduce their own digital currency is probably the moment when privacy completely dies for its citizens.