Scopes can be refreshed by the administrators of the system by double clicking on them and having them resolve. Otherwise you can logon to the server and in the Configure -> Services area under Scheduler tab, you can set the interval of when they should be resolved.
Also a user can refresh the scopes manually in the very top toolbar by clicking on the icon with 3 colored circlesoverlapping each other
Using Scheduled tasks, it appears that the LDAP query is only validated against the correct LANDesk object, when that object has updated it's 'LDAP Location' attribute...
Why would we use then the LDAP query functionality?