Try granting "Send as" permission and see if the Calendar behaviour changes.
http://office.microsoft.com/en-001/o...010075081.aspx
"There is an advanced Exchange feature that allows one or more people to be granted Send As permissions for another Exchange mailbox. This allows someone to send a message as if he or she is the owner of the mailbox. Send As permissions can be used with or without Delegate Access. When Send As permissions are enabled, the recipient will see only the manager's name next to From. An Exchange or Microsoft Windows administrator must configure this option."
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