The purpose of the "Great FIrewall of China" is to censor the Internet, i.e. the intention of this MITM doesn't seem to be to covertly spy on the University user's searches.

A self signed X.509 cert is enough in order to see what they are searching for and to block/RST queries for topics like "Tiananmen Square protests". The CH authorities don't care if users notice the MITM in this case.