QCS creates stub objects in AD as expected, however they are not visible in GAL. The objects can be seen in the Exchange Management Console, but they will not appear in the GAL until the "Update-GlobalAddressList" command is executed in Exchange Management Shell.
Objects created by Collaboration Services in Exchange 2007, 2010, 2013 need to be processed by the subscribers RUS (Recipient Update Service), only then will they appear in the GAL.
1. In the Collaboration Services console right-click on Collaboration Services and select Properties
2. Expand General
3. Navigate to RUS and on right side select the checkbox that says "Use the built-in service to stamp mail attributes on stub objects"
Note: Leave this option unchecked for Exchange 2003
