When you look at their coverage map, it appears that they're buying network access from just about everyone and using quad band phones (?) to give voice access pretty much anywhere. Their data network is EV-DO so I suppose Sprint and/or Verizon.
There isn't much detailed info on their web site. Their plans seems a little high, but if you can voice call without roaming charges from basically anywhere, it might be worth it. Just looking for better information.
It's never too early to begin preparing for International Talk Like a Pirate Day
"The software I buy sucks, The software I write sucks. It's time to give up and have a beer..." - Me