I was exploring the newly introduced town of Svetloyarsk, specifically its police station. (or some 3-story building with a jail cell inside -- it was difficult to tell during nigh time). I opened the jail cell and entered easily, as with any other doorway. Upon trying to exit the jail cell, I was unable to exit the open door as if there were an invisible barrier preventing me from passing. I managed to "escape" by sprinting through the door while also shutting the door, which appeared to force me out. However, this was not without many failed attempts and a few frustrating minutes.
As fantastic of a prison this would make, with inescapable jail cells and all, I expect this is not the intended functionality of such a jail cell for DayZ.