@Hudson, great point! I thought you could "re-tool" the standard MTH offerings for 2-rail but, don't know anyone who has done so successfully. It makes good sense.
The reason I reached out to Joe @ Baldwin is because I am getting the new MTH R-142 subway set which only comes in a 3-rail version but, obviously I would need to get it to 2-rail. I have never attempted a conversion myself and am very hesitant to to start out on a brand new set with PS 3 in it.
I wonder how difficult it is. If not too crazy it opens up a whole world of possibilities, though many of those vehicles are not "scale", I'd rather have them running than nothing at all.
Chris, yes you are correct, you can re-tool any of the standard MTH offerings and Joe at Baldwin is the guy to go to. He has done many of these. I didn't realize you wanted to 2 Rail a subway set. I just didn't want you to send out something you could do yourself. With the Subway set or any other standard 3 rail locomotive that has a standard diesel truck (excluding steam) if you don't want to send it out to Baldwin you could try to convert it yourself. In O Scale Trains issue #53 John Sethian wrote an excellent article on doing just that. I have read it twice and I believe I can do it but I haven't tried it yet. If that issue is no longer available as a back issue then you should be able to download it for free at the O Scale Trains website.
Another thing to consider is, like you I prefer DCC, not that I have anything against DCS but since I have other DCC locomotives I like to control all of my locomotives with one remote. It is true that any MTH item that is PS3 has a DCC decoder built in. However, I am told that locomotives such as Railking do not have a DCS/DCC switch on them. I don't know if the subway sets have the DCS/DCC switch. The good news is there is a way to add the DCS/DCC switch if the locomotive doesn't have one but the bad news is I do not know how to do it yet. I was told that I must contact MTH Tech support to find out how to do it.
If you find out how to add the DCS/DCC switch please let me know. From time to time I have seen a RailKing scale locomotive that I wouldn't mind owning.