Western Washington was always a partnership between the principles of Frontier Rail and Nexxtrail. Frontier bought the underlying track and shop at Western Jct from the City of Tacoma. It ended up that the Western Washington partnership was dissolved, and Frontier operates the line under WRL/Rainier Rail.

About the same time, Frontier's Lake Railway was leaving Lakeview, Oregon and the Modoc line. Successor operator Goose Lake Railway is a partnership between Nexxtrail and one of the shippers in Lakeview.

Regarding previous posts about Frontier's contract switching operations for Railex now UP Cold Connect - at the expiration of the contract UP awarded the bid to Harbor Rail Services instead. Frontier may have leased their engines to Harbor until their own were delivered. The former UPY 1299 at Wallula is now in Walla Walla, I believe the former UP 1284 from Delano went to Western Jct? Not sure what was in NY at the end of operations, if it was Frontier's it likely went to their CCET in Ohio.

Disclosure - I worked at one time or another for many of the above companies.