These were part of the Williams Masterpiece Series, along with 2 NYC Hudsons, streamlined and unstreamlined (I have both); there was also an SP Cab-forward, I believe. This was,
unfortunately, Wms last gasp in the brass business, but it was a good one.
They are rare, but seem to go for moderate prices when they do show up, at least the last ones I noticed did. This was a few years ago. I'd grab one if I were you - I seem to recall
They can certainly be upgraded to any system that you would like; essentially a model
locomotive is an empty shell, a motor and some gears, and the electronics used to run it can be of any type that can run (in this and most cases) a DC motor. I use ERR Cruise Commander/Railsounds.
There's nothing special about these things; anything can be upgraded to anything if
you remove the old "system".