You have the right idea by draggin the parts lists over. That is the easy part. haha. Now you have to map to the correct Pipe Catalog.
When the other employee made all the parts it would have been mapped to a different directory than your 2011 Civil 3D.
Re open one of the older drawings that you know worked (Open in 2009). Check that Catalog Directory. Thant will be the one that was modified for the Parts List. I would suggest you copy that one to a general location on the server for all users to refer to.
When you copy it, all you need to do is copy the ENTIRE pipe catalog folder. You will need all of the files within it for it to work.