Finished reading the Classic Trains magazine detailing all the Lionel dealer demonstration layouts. I know that OGR published an article where Jim B. built one using fast track as close replacement for Super O.
Granted these layouts were not complex, and designed to run trains in circles and animate alot of accessories for show to draw people into the store.
As aside, growing up in Pittsburgh in early '50s, my Christmas high was going to Horne's, Kaufman's, Gimbel's, and Boggs&Bhul's toy departments to see those trains. Of course being 8-9 YO at that time I couldn't tell you if those layouts were Lionels or store built, but to a little tyke they seem IMMENSE!