While yesterday I made a list, I was thinking a bit as to some good points of Phil's initial question as to what role a private/estate railroad or collection has in long-term preservation.
Ultimately, I believe the role of private collectors and full-scale backyard operations is far more important than first meets the eye.
Let's go back to, once again, Ward Kimball. While it was (and is to this day) painted and lettered for his narrow-gauge empire stretching merely hundreds of feet, I don't think you could say a single piece of equipment he owned was 'common'. The old Barney & Smith coach that he purchased from the SP, dating to the Carson & Colorado; would have been BURNED! The Nevada Central #2 wouldn't have been "Emma Nevada", it would've been held in no higher regard by a junker than anything else and cut up. While due to Mr. Kimball's popularity and notoriety the GFRR may be the first thing that comes to mind when looking at any one of these pieces, his gift to the Orange Empire has ensured safe preservation so the equipment can be enjoyed many years into the future.
Bud Hurlbut, a theme park designer and miniature train manufacturer, owned the Virginia & Truckee #25 for some time before he sold it to return to Carson City; and later be returned to steam by Chris DeWitt and his crew.
There's a million other examples, too. Just yesterday I began writing an article on the history of the 3' Pine Creek Railroad in New Jersey. All started with one New Jersey railfan's acquisition of a little 0-4-0T working in the sand pits south of New York City. This brings another example; when something is 'too common' or 'too far gone' and brushed aside by another group. The little teakettle Jay Wulfson started his operation with was sold for scrap; the junker advertised it for sale, and he got interest; from Disney! For several years, this locomotive was owned by Walt Disney himself (along with Disneyland's other rail-related attractions) and his personal company, "Retlaw Enterprises". ('Walter' spelled backwards).
Most of this equipment exists today because of railfans with deep pockets of both cash and time. I'd say the preservation world owes a great debt to many of these guys for what they've done.
