I tried the diversion, and it worked
Here is how I did it: when you're in the cells corridor, exit it toward east, turn right, then right again. Follow the corridor, you'll arrive at an intersection with a corridor on your left (south), red squares (zone change) on the front (west), and a vent trap on the right (north). I threw a grenade as far south as possible, then blocked the way from the east with a psi force field (to force tchortists to have a longer path to go at the grenade location and buy a bit more time), and then ran (with sprint ability + combat mode) in the vent. From here you go north and out of the vent; you're back in the cells corridor (you should open the cell gates before throwing the grenade), go quickly talk to Sharp so that they leave... And they were able to, just before the guards came back.
I double checked that Tchortists didn't know it was me ; going back to the university they didn't attack me, everything still normal. Another good hint is that it didn't trigger the tremors.
So, it feels a bit hacky and almost an exploit, but it works. I don't know if the psi force field was necessary or if it can work without it. Don't use traps to block the way because as soon they see the traps (even if they don't get hit) they turn hostile (i.e. tremors start). Also, you can use caltrops to block a way (if they see it they'll take another path sometimes), without turning them hostile, but if for some reason they walk on it (and they do more often than not), then they do turn hostile.
Also, I don't think there is a quest related to this event, but maybe I'm wrong? And out of curiosity, is there a way to see them again later?
