I was surprised to see when I read 'Microsoft launches Live Search Webmaster Portal beta' at LiveSide. As recently invites were sent for the same mentioning it as private beta.
But ,now anybody can try it out at http://webmaster.live.com/ logging in with your Live ID.
It first asks for the profile setup with a verification step where you have to either choose uploading a xml file or inserting a meta tag. I am yet to try it out further.
Check LiveSide report for more details.