I'm a realtor, but also work in a large development firm in NJ and PA. We have a number of communitites in PA. What I've seen done a number of times is what I call "dummy listings". For example, a national builder is now building in one of our developments. They created 4 listings for 4 different floorplans, 1 MacDonald Drive, 2 MacDonald Drive, etc even though these addresses don't and actually never will exist. In the end when the job is closed out, they expire the listing.
Hope this helps.