While steaming Walnut (and Beech too, btw) is a very old way to darken the sapwood of that tree, that place in Billings doesn't do that. That's just their kiln operation and they don't steam for color. They haven't handled walnut for a long time now and won't in the future either. That place is selling everything out and just doing hardwood (red oak and a little maple that they get elsewhere) flooring. The Billings operation does the roughcut and kilning and then sends it on up to Springfield for the milling.
I suppose you could use Sycamore for RR ties but I don't know of a single tie maker here in SW Missouri or NW Arkansas that use it. It's not a wood that's going to hold up in that situation very well at all. It's mainly Red and White Oak that's used around here. Maybe the Sycamore logs you saw where mine. I do a bit with Sycamore.
- Andrew