> But would love to know what, if anything, they
> did to 3985 sitting in the roundhouse.
> Did they bother to cover it?
Yes, they did cover it. That's the "in the roundhouse" part. Indoor covered storage. The best way to preserve vintage rolling stock, and in fact better than a cover directly on the locomotive that traps moisture. Then again, they may have put some tarps on her to keep the bird droppings off, I don't really know.
> Any special treatments or moisture-absorbing materials
> in the boiler to minimize corrosion?
I don't know, but I doubt it. Some places would put a small heater in the firebox to keep the dampness away, sometimes just a light. I doubt UP did even that but I honestly don't know. Cheyenne is cold, but the air is fairly dry, and it probably wasn't an issue.
The boiler shell isn't going to rust significantly when stored indoors and dry. You're going to change the boiler tubes anyway when you return her to service, so not a lot of worries there.
> Keep oil in the cylinders and bearings to minimize corrosion?
I'm sure they did that.
> Back then, did they consider that they may someday bring
> the locomotive back into operation?
I don't know for certain but possibly. If you recall 844/8444 was never officially taken off the active duty roster. So they've always had a corporate culture that respected the steam heritage. Did they put away 3985 because it was historically significant, or was there hope to some day run her? I'd be interested to know the answer to that myself.