While gathering more info for my Japanese vacation that will happen someday, I happened upon this Wikipedia article. This is another new museum within JR West's operating area, apparently to be operated by them and to open around the same time as the new Umekoji museum. Some of the rolling stock is from the Osaka Modern Transportation Museum.
https://en.wikipedia.org/wiki/Tsuyama_Railroad_Educational_Museum
https://www.westjr.co.jp/press/article/2015/10/page_7843.html