If you are interested in changing the permission level (Read) for the default user from showing free/busy only to showing limited details (Free/busy, subject and location) on calendars of resource mailboxes, this is possible with the use of “Set-MailboxFolderPermission”  , more details here http://technet.microsoft.com/en-us/library/ff522363.aspx

 

Example: Meeting room1

 

Set-MailboxFolderPermission -Identity MeetingRoom1@contoso.com:\ calendar  -User default -AccessRights LimitedDetails