The Tiananmen Square protests were in 1989, well before the rise of widespread internet usage, I wonder if given the speed with which information moves around these days if the government of China would risk a second confrontation in the public eye like that.

While the OP states clearly that the government is doing a lot to crack down on communication with foreign entities I can't help but think that communication inside China is still on average a lot faster today than it was in 1989.

Are mesh networks illegal in China?

Nah, they'll stop the tank and show their mercy to the international public, while an onslaught of protesting students is going on outside the view of the camera. Then you'll get taken away by a man on a bicycle and never heard from again.