This is pretty surprising that AT&T engineers were the ones to design the antennas.
It is usually vendors such as Nokia-Siemens, Alcaltel-Lucent or Ericsson that provide the equipment and that have the antenna/radio know-how while on the operator side the engineers there focus more on optimization and RF planning, rather then the design.
If you watch the video of the two AT&T engineers, they basically say that they just had the idea; their (unnamed) vendor actually did the work to see if it was feasible and designed the antenna.
When you get to the level of "top 5 customer" (which AT&T almost assuredly is to whomever their equipment vendor is), the customer has quite a bit of input into the design of new products. Especially if the product is going to be sold primarily TO that huge customer.
