In Arma 2, when you were next to a group of players from another team, or side, if they talked using VON in group channel for example, their voices would be broadcast also to the same effect as with using direct channel.
This was realistic as speaking down a microphone in real life would still allow you to be heard directionally to nearby people.
In A3 this is not the case. It seems now that when you speak in another channel other than direct, people in different groups cannot hear you locally / directionally.