No idea, but the only sane way I can think of is to try and hack (crack) some "base" systems which are not hardened. That's stupid too, because (at least in the Linux side of world) there are a lot of distributions => combinations, so it's not the same as a Windows or Leopard OS - one combination of Linux operating system could be different from another. Or if they allow hardened operating systems, where's the limit - what prevents them from sinking their Vista boxes in 10m thick seamless metal containers that won't open without some heavy machinery, or encrypting everything and eating the key?
Well, I hope they've got some sensible "rules" there that try to make the "contest" fair between the three..I doubt if it's possible, but anyway. All of them have their own strengths and weaknesses that aren't, in my point of view, comparable.
Will be interesting to see the results, however..