Just found that Calif State Railroad Museum posted this 42 minute YouTube, showing you the "Magic of Scale Model Railroading" exhibit.
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The video is specifically made for a general audience, i.e. someone who is on the Calif State RR Museum YouTube channel and happens to wonder "what is this all about"?
The overview of the HOn3 San Juan Central by Malcom Furlow, starts at 8:01. (It's Charlie Getz speaking at this point, he is one of many primary NMRA'ers behind this 15-years-in-the-making exhibit of Scale Model Railroading). The 40 foot long "Wall of Trains" is shown at 13:45. Basically the first 20 minutes walks you through the exhibit. Starting at about 23:00, interview with Charlie Getz and how the exhibit came to be.