I am a collette communicator user. It is the only brand I am familiar with. I have used them since 1989. We Newfound Snowworks were the exclusive dealer for New England for a couple years 1989. The quality is good and they do work. It is not like talking on your cell phone in your automobile, but it is good. We have always had our own code, limiting communication to one or two signal words."Incoming", meaning sleds approaching etc. When you are stopped at an intersection you can all sit on your sleds and talk without removing your helmet.
I THINK 2 miles is pushing it but certainly 1 mile is accurate. If you travel in a group and are speed out properly you can relay communications.