Re: NG Interchange

Yes I recall having seen a few such photos, I do not recall where though, as my interest lies with the 19th century roads. From almost day one, of the DSP&P becoming operational, the D&RG and DSP&P were interchanging cars, and it went from there. You simply have to look closely and you will eventually find some.
Photos that I recall. Santa Fe box cars in a string of DSP&P cars on a branch siding of the D&RG yard at Buena Vista. F&CC cars on the Boulder narrow gauge. D&RG and DSP&P cars in Clear Creek canon on the Colorado Central. Utah & Northern and Colorado Central cars on the DSP&P Baldwin branch. A D&RG box on the Denverm Utah & Pacific, or was it the Denver, Longmont & Northwestern. A Kansas Central box car at Morrison, a Kansas Central baggage car in Boulder canon, are a few examples
When UP converted the Utah & Northern and Kansas Central roads, they shipped many of the cars to Coloradom where they were used on the DSP&P and Colorado Central roads.
Researching the old records reveals a D&RG business car taking a trip over the U&N into Montana as the VIP didn't want to change cars. RGS cars on the D&RG / C&S / B&M / F&CC / Silverton / SG&N / SN / Pagosa Lumber / Lumberton
I found a book of cars received D&RG, I beleive at Divide that lists several DSP&P and at least on Colorado central car passing through. IIRC one of the DSP&P cars was coming from Aspen
In short, there was some interchanging of cars between the roads through out most of the narrow gauge history
Ron Rudnick