http://en.wikipedia.org/wiki/Amateur_radio_frequency_allocat...

While the 40M band beats the curvature of the earth quite reliably, I would expect that they are doing something in the UHF band if they plan on deploying this in licensed cell-phone frequencies.

Also the amateur band lets them transmit at much higher power than the ISM bands:

http://edocket.access.gpo.gov/cfr_2010/octqtr/47cfr15.245.ht...