The listing for a full track plan doesn't have all that much new information in general - the scan isn't that great. Though there are some detail shots that have a little bit of notation on the plan legible for track radii and the like.
The same goes for the Lilly Belle schematics - lower quality scan means not much can be gleaned that can't already come from fan produced plans.
What had me more intrigued was the listing for Carolwood Pacific Railroad Trestle Bridge Artwork were not something I'd run across in the past, and the scans are beautiful. Take a look at this:
Not a hugely complex design, but nice to see the original drawings nonetheless.