I found this train of a couple of locomotives, a decent-looking SP caboose, and maintenance-of-way equipment. The lead locomotive was for the Albany & Eastern Railroad, the short line that owns the track that runs through Lyons (near Mehama) up to Mill City. The other locomotive was marked RFRX, which appears to be the reporting marks for the Rick Franklin Corporation, a company that includes railroad interests. Based on the shared logo, I'll speculate that this company has acquired or has an interest in the Albany & Eastern.
I spent only a few minutes taking train pictures (more starting here) before getting back on the road that led to Yreka.