I live in China, so I did a quick test with my coworkers. 4 people. Two phone calls each. Each conversation we dropped the word 'protest' in both English and Chinese. No magical dropped calls for us.
Chinas telecom and internet monitoring and blocking is regional, what may be blocked in one region may be available in another, although there is certainly some centralisation of this system.
The goverenment is certainly experimenting with such a system in one or two regions, along with their pervasive cameras and face recognition.
However, seeing as the government here seems to have some difficulty building a road on time, on budget, that is actually decent quality it seems unlikely that they'll get this working.