There is an open invitation to all players, with the exception that teams have at least 2 Oceanic players in their roster. Oceanic in this case means strictly from either Australia, or New Zealand.
The ladder kicks off Sunday, October 17th and will be 8 weeks long. After Christmas, two finals series will be played for another 4 weeks. The prize pool is $1250, split among the top 3 contestants.
Registration has begun today, October 13th, and the link for registry can be found below.

Links
CyberGamer.com - Ladder Registration
HoN Forums - Event Information