Each service elevator here is shared by just two apartments, and is at the point where the kitchens match up to one another (most units have large kitchens where the "maid's room" has been merged with the kitchen space, but I guess there are a few with a small extra bedroom still). In the pic here (click for bigger), the elevators are at the inward right angle points, the indents on each of the corners, and around the central core.
Some of these get a lot more traffic than others ... one goes right down to the door to the garage, for instance, and others provide a short cut to stuff like the pool and garden. I've been using ours to get out faster, as it lets out in the commercial area, which lets me exit out on Sheridan real close to the bus stops, saving me nearly a block's walk to the main elevators (in the center of the building) and then to Bryn Mawr and back over to Sheridan.
Speaking of "staff" and the pool ... there's a big patio area up from the pool that used to be a restaurant (with full kitchen that still exists), which was primarily used by residents on those one or two nights a week that their servants had off ... since they couldn't possibly be expected to cook for themselves, could they?
I do sort of wish the restaurant was still there ... but it might be a bit creepy to be going for a swim and, essentially, being "the entertainment" for those in the dining area!