It should be noted that players outside of a certain distance, ca 2km, are not able to hear eachother either, on the custom radio channels.
This counts for players spawning in at a distance, as well as players spawning close to eachother, then moving away until they reach the apparent max distance from eachother.
This only affects voicechat. As with the vehicle issue, textchat still works as it should.
I uploaded another test mission (OUT_radioTest_02.Altis.pbo) wich will allow for testing this aswell.