Police arent allowed into the campuses thats why the soldiers entered dressed as students in the 68 massacre, Autonomous is more about being allowed to do their own thing or more like organized the way they like, here is a doc that talks about it
PRI ruled in Mexico wasnt like Pinochet in chile that was a autocratic police state, the Mexican Political sistem was design so that the 3 powers that be (president, party and syndicates) would be united under the president but still allowed semi-autonomous organizations under it.
there was a big break in the PRI between the left and right factions, the Right won but due to the fears of a communist take over, the worsening of the material conditions and the decay of the 3 powers sistems, they started to harder and harders crackdowns on potencial enemies culmination in the 68 massacre planned by Echeverria then governor of the capital, in a ploy to set himself as the presidential successor (because back then the president would chose their successor).
hope that helps
Today i survived on 2 hours of sleep
but i also ate chinese food which was very good