If they have the public folder available in their outlook they can use Desktop Manager to sync it via USB. They will have to go into the sync settings and select the public folder instead of their Address Book and also set it for one way sync, outlook to the BB only. Before this will work they will have to turn wireless sync off for the address book on the BB because a wired sync will not work while the wireless is enabled.
Use the following KB for instructions: BlackBerry Search Results
This should help.