I did it in HOn3. As a part of my basement layout, about 15 years ago. I had a large L shaped HO railroad, with a connection to a dual guage "TimeSaver" at one end of the layout, and a narrow gauge line going up into the mountains from there.
It was quite fun running a broad gauge train around the layout while switching the dual gauge. It puts an interesting twist into the timesaver, that's for sure!
I used either an MDC Consol (I had two, the inside and the outside version), or my narrow gauge MDC Shay. I also used a Bachmann 44 tonner in D&RGW livery.
I've given some thought to trying to convert one of Bachmann's 1:20.3 narrow gauge 45 ton diesels to broad gauge (4' 8 1/2) and perhaps scratchbuilding a couple of F scale cars to go with it. The Warrior Run flat car would make for an easy conversion, and I believe someone makes an F scale boxcar...
Of course, this would require scratchbuilt dual gauge F track...
Edited 1 time(s). Last edit at 11/02/2011 10:27PM by rdamurphy.