What is a "real" railroad versus an amusement railroad is a gray area. I do consider the Maine two-footers as "real". It is obvious that there were some smaller gauges that acted as railroads also. Wasn't there a smaller gauge railroad in the UK that hauled schoolchildren on a regular basis, and even had an armored train complete with anti-aircraft guns in WW2? I believe it is still operating.
On the other hand I have seen a 36" gauge train operating in a park with a Crown 4-4-0. Truly these trains and most "live steamers" are built for amusement purposes, and are not comparable to the trench railroads of WWI (for example).
Even the #12 at Georgetown Loop had been a "gray" engine. Silverwood was using some kind of system typical of trucks and it wasn't even equipped with a front brake pipe. Its firebox was a disaster with an absolutely useless arrangement of the firepan and firebrick, but evidently worked good enough for Silverwood's service. #12 had to be converted back to a "real" engine in 2005 compared to the previous standards that it operated under.
I think that what standards and purpose the equipment and railroad was built for should be considered in determining what is a working railroad (even if it does just haul tourists) veresus an amusement railroad. Scale railroading is interesting, and I have pleny of HO scale stashed for a rainy day project. My large scale interests jump to 1:1, just a little more expensive!