When I added all of the tracks from our server to my iTunes library, I had a lot of duplicate tracks. On my laptop, I had the protected AAC files, and the server has the mp3 format versions.
First I used iTunes "Show Duplicate Tracks" menu item to display all of the duplicate tracks. Then I selected all of the tracks and created a playlist with those. Then I ran this script which puts all of the duplicate tracks that are located on the server into a new playlist.
Then all I had to do was delete the tracks in the "toBeDeleted" playlist.