Linkedin does not use any solution that would presist user state across subdomains, i.e. you can be logged-in on www.linkedin.com and logged-out (looking at the registration form) on nz.linkedin.com. Or any other country-related linkedin subdomain.
In other words, you can display somebody's profile browsing through main domain (e.g. http://www.linkedin.com/profile/view?id=66666666) and you're logged in. But when you use the very same guy's national URL (presented below his/her photo), e.g. nz.linkedin.com/pub/some-guy/1/235/567 you'll see a form asking you to either login or register a new account.
What a lame!