There is obviously a good bit of research in these posts but I see no point in stating that the Como crews are building a "train set".
I've been involved in rebuilding a narrow gauge railway for 20 years and much time is taken to correctly replicate track structure on the original grade and buildings on their original location. It's a rebirth of the original operation with pieces of original rolling stock and one locomotive. The Como project is the same thing except that they have original structures to compliment the railroad. I consider the Como track to be a rebuilt portion of the D,SP&P yard and mainline (although some may say it's more C&S). Either way, the excellent work being done brings back a lost treasure.