Saw some other elevators with those as well. Although I never found any, found it difficult to tell whether you need to select different dialog options to get them, do certain gigs or they being missing content.
I found this months back. The keycard is needed for access to the roof of the ncpd building. You have to some parkour to get on top of the building but when you do you will find that floor is the one for the ncpd building roof av pad. I think there is a planed mission for the dlc there. There are few more locations like this where you can see place holder assets.