The basement floor where the captured espers were detained was different from the detaining room in the Trinity compound.
There was no nice dorm room with adequate amenities. Here, it was a proper iron-barred room with a single bed and a desk. The light was bright enough for the guards to see them clearly, and the only privacy they had was a small bathroom in each cell.
Unlike a real prison, however, the bed was fluffy enough to be comfortable, and they were given adequate meals as well as entertainment such as books and board games. The captives were provided a change of clothes regularly, with a bonus of ability-sealing bracelets and mobility-restricting anklets.
All in all, except that they couldn't access the outside world, they didn't exactly live miserably. At least, they were meek now after a few weeks.