In legacy versions of Exchange Server we could use PFDAVAdmin to manage calendar permissions, or alternatively the 3rd party tool SetPerm.
With Exchange Server 2010 calendar permissions can be managed using the *-MailboxFolderPermission cmdlets. While these cmdlets can be used to manage permissions on any mailbox folder, we`ll focus on calendar permissions.
In fact we got 4 *-MailboxFolderPermission cmdlets in Exchange Server 2010:
Since I`ll be focusing on managing default permissions , which is an existing ACL on the calendar folder, we need to use the Set-MailboxFolderPermission cmdlet:
To grant “Reviewer”-permissions for the “Default” user, we would run the following:
Some companies have a policy that everyone must share their calendars with all users. Since it`s now possible to manage calendar permissions using PowerShell, I`ve written a script to accomplish this task; Set-CalendarPermissions.ps1.
While this script could be scheduled to run on a regular basis, a better approach for managing calendar permissions for new mailboxes are the use of the Scripting Agent which is a part of the Cmdlet Extension Agents, a very useful feature introduced in Exchange Server 2010.
(source : http://tinyurl.com/7lg3umf)