The backdated version of the Montana Hi-Line route is now available on the Steam Workshop.
You can subscribe here:
https://steamcommunity.com/sharedfiles/ ... 1977906262
Scenarios are available here:
http://golden-age-rails.com/rwscnrio.html#greatnor
They are also available here in the RWA file library.
You must own the Montana Hi-Line route from Steam (US or worldwide version), and the installation of one external asset pack is required. Please read the installation instructions on the Workshop page for more details.

Cheers
Michael