The movie is pretty grounded in reality (at least where the towers are) so I figure they must be based on something real. Unless I wasn’t paying attention they don’t seem to be anything obvious as shown in the movie. They look about three times the height of the apartments, so I can’t imagine they’d be like birdhouses or anything. They also look to be only around the area the apartments are in, so probably a relic of whenever they were built?
The only thing I could think of was maybe a weather siren or a shelter? But I don’t think you’d need a giant concrete tower for either…