I thought you might be interested in seeing some of the strange things I have observed as a consultant for healthcare organizations. This is a picture of a cage that a hospital built inside the stairwell. It was their attempt to create a locked door to prevent access to the roof.
It was successful in keeping unauthorized people from having access to the roof but it is not compliant with section 126.96.36.199.4 of the 2000 LSC which says you cannot lock doors in the path of egress. Also, section 188.8.131.52.3 says you cannot have anything in the stairwell that could interfere with exiting.
A cage with a locked door would certainly interfere with exiting.