You can access Portal in browser now it seems but only to piss about with. You can create an 'experience' which does appear as in the screenshot below. I haven't yet managed to get to the rules editor which is the part I am most interested in.
I don't know if anything created here will actually be usable when it all goes live, or if this is just for playing with only.
There doesn't appear to be anything I've seen yet that allows you to setup admins at this point, so I am assuming you do that once the server is up....we'll see I guess.
review.portal.battlefield.com