Brian, thanks for the images of the cellular phone/data towers. I've been seeing similar 'equipment' on old water towers atop old factory building in and around North Philadelphia. I figured they had something to do with new signaling, but I didn't surmise that that is how cellular works.
The positioning of this equipment here upon often vacant old buildings is an interesting aspect of how real estate value (or at least rent value) can suddenly change and/or suddenly 'materialize'. It reminds me of how other older, vacant building are still generating income because the have large billboards on their roofs or on their side walls.
I agree with your concern of the possible ill effects of such concentrations of em waves.