All tasks in Exchange Server 2007 or Exchange Server 2010 can be done in the Exchange Management Shell. So you are also able to give the Send-As permission and the Full-access permission via the Exchange Management Shell.
Send-As permissions
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.
After installing and configuring the Blackberry Enterprise Server application you will need to run the following Exchange 2007 PowerShell commands to grant the Blackberry service account (besadmin) access to the Exchange mailboxes.
In this example we are giving the besadmin account the access required to handle the email for the john.doe@domain.com mailbox-