Apparently there is a way to make the prisoners in Moonrise Towers disappear, sadly:

Quest: Resue Wulbren (Moonrise Towers)

If you try to sneak into Moonrise Tower and attack the single guard on the north eastern side Outside (near the broken Bridge), you can choose to go willingly into prison. That works and you can even escape the prison (Misty Step) an get your loot back BUT:

All other cells are empty. No Wulbren, no tieflings. Also they dont return at any point, so there is no way to solve the quest. They are simply not there, the whole prison is empty except for the ememies. Later, of you talk to Barcus, he acts as if Wulbren is just dead.