In all the research I did while putting together my big McCloud River book, I only found one real references to any proposed mainlines through that corner of California. In 1888/1889 the Union Pacific ran a survey from northeastern Oregon southwest across that state, entering California somewhere around the far northeastern corner and then more of less following the route of today's Highway 299 down to the valley. UP bought some land on the route but never built anything.

When Hogg's Oregon Pacific was building east the general reports were that it was heading for a connection either with the Oregon Short Line or a westward extension of the C&NW somewhere in southern Idaho. I doubt the C&NW would have had any extensions towards the UP Burns Branch, as that didn't come around until the 1905ish time frame.

Jeff Moore
Elko, NV