Aparently a Beotalk 1100 was tried and failed.
There are many differences between the US and Aus Phone systems. If you get past the voltage problem. Potential problems include it won't answer all calls, be clear, have random problems and remote access won't work. Austel which certify phones for the Australian market have very different requirements than the US.
There was some talk about a service mode on the unit to change it from one country to another but I'm not sure if this was ever implemented for the US units if at all.
Will it work guaranteed? I don't think anyone knows... Speak up if you do.
Beoaus.