my guess is satellites or communicating with other cell towers but the latter seems counterproductive as it would push a high load to a different cell tower. but if they used satellites, wouldn't there by high latency and bandwidth limits?
From what we would could see, there were a bunch of ancient racks running 2g gear that looked at least 10 years old (all beige), and then a whole 42U rack of 12v batteries for a UPS.
Then there was a quarter-rack which had a bunch of fibre cables going into a few Huawei branded 1u boxes. LTE only got deployed a month ago so it much of been HSPA+.
I think if they had a satellite connection there would be too much latency. And the throughput wouldn't be limiting as well. They could of had one as a backup source though, or just setup as a secondary connection.
I think ATT is a tier 1 network, so your connection to whatever data center will probably get bonded directly to whatever ATT datacenter which has the fastest response (ping) to the content your connecting to...love to see a traceroute for comparison.
http://www.huffingtonpost.com/2013/01/07/cell-phone-towers-i...
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.
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.