Not going to be happening soon. Every Mainland politician in charge of some kind of HK affairs would be out of a job. Liaison Office, SAR govt, HK-Macau affairs office etc. Those people know how to protect their interests. I'm sure the central government is fully aware of the impact the PLA will have. Even with a full riot and burning cars the PLA will be a long way off. The HK police is fully capable of handling it themselves, once they have an excuse of going postal on the protesters.