HD,
In Oz, our comms, intercomms, phone etc are all handled by one touch screen located below our weather radar and ops info screen. It's called a VSCS (Voice Switching Communication System, I think). All voice, alarms, and other tones come through your headset and no diferentiation is made for which earpiece.
So whether it's phone, intercomm (hot or cold line), air ground or alarm/tone, if you have a double sided headset, it comes through both earpieces.
http://www.airservicesaustralia.com/...banecentre.asp