The StarCraft 2 blog carries word
a new feature is coming soon to Battle.net - region linking:
Region linking will benefit players in the connected regions in a number of ways. First and foremost, a linked community means a larger pool of players to improve our automated matchmaker. Whether you're an elite Grandmaster or a Bronze-league all-star, more players in the mix means that we'll be able to find you a matchup more quickly and more accurately. Players will also get access to a broader range of custom map games, which in turn means wider audiences for mapmakers. Those of you who have friends in the linked region will also be able to add them to your Battle.net friends lists once the region linking is complete.
The post also carries a FAQ with some more information, although nothing about Australia is mentioned specifically.