I've seen line-of-sight microwave used for similar needs, but not in built up areas.
Edit: clicking through and actually reading the link, the picture clearly depicts Microwave backhaul. Probably to a site in the vicinity they have a nice big land-based pipe.
The article describes the microwave link as 'additional capacity', so I'm guessing that they had another (primary?) connection, but needed more throughput.
When the rugby world cup was running last year I saw a number of temporary cell sites, which had plastic ducting and fibre optics running ~50-200m to existing telecoms cabinets or cell sites.
I imagine that At&t is doing something similar, hooking into an existing cable at the nearest roadside cabinet or traditional cell site.
Edit: clicking through and actually reading the link, the picture clearly depicts Microwave backhaul. Probably to a site in the vicinity they have a nice big land-based pipe.