Sharepoint - Exluding some users from Search
This can be achieved by using Search Scopes.
You will have to create a custom search scope (Eg:"People Search") in Search settings of the site.
Add a rule for the scope and select Property Query as the scope rule type.
If you have an AD property that is set for users coming from the phone system, select that property and select the value that is brought from the phone system. (If you dont have a property added in the scope, go to CA, Metadata properties -> UserName -> Edit/Map Property. Click the Allow this property to be used in scopes checkbox in the Use in scopes section.)
Select the behaviour for the rule as 'Exclude'.
Add this scope into the default scopes dropdown for search.
You may need to wait a few minutes for the scope change to update the search results.
Central Administration > Application Management > Manage service applications > User Profile Service Application > Synchronization > Configure Synchronization Connections
Click on your connection, Edit Connection Filters.
Here you can exclude users.
http://www.harbar.net/archive/2011/02/22/323.aspx contains some more details of how to exclude disabled accounts etc.
By excluding the accounts user profiles are not created and therefore are not indexed so do not appear in the search results