You guys are getting hung up as if his results need to be over a whole borough or the whole city. In reality, if he is getting performance like that it is likely isolated to a specific site. He likely has a strong signal, the site is under burdened and has fantastic backhaul. But it is possible.
Most WiMax sites speeds are limited because of backhaul, not because of the air link. The WiMax Protection Site here in Santa Fe is AAV and maxes out at 10Mbps. However, some WiMax sites that feed multiple sites with microwave can have a fiber or high speed AAV link. You find one of these that is under burdened and you will likely hit the max speeds around 16Mbps.
Robert via Samsung Galaxy S-III 32GB using Forum Runner