Open calendar -> from adress book Function in Outlook should add calendar with correct permissions not busy/free
If you open an other users calendar which is shared for you with Administrator permissions, the calendar should be displayed correctly when you use the "Open Calendar" -> "From address book" function in Outlook.
Actually the users only see free/busy informations when they add the calendar this way, even if they should have Administrator rights.
Thats one of the main reasons why we still have to sell Exchange Mailservers to our customers which use Outlook and some of it's really useful features in combination with Exchange.
Or as an alternative: to have at least the Option if you add it through the Other Mailboxes Register, that the account isn't displayed under the Mail view, when you only have access to the calendar... It's a bit ugly if you have a lot of calendars shared for you and you have to use all of them from time to time... there a big list of empty mailaccounts in the mail view, not user friendly :(