The Modoc Northern had essentially two operations- they started by leasing the Klamath Falls to Alturas line from UP, and then after a fairly short while Lake County struck an agreement with them to operate their Lake County Railroad. I don't remember the exact sequence of events, but when the MN imploded UP cancelled their lease and then almost simultaneously the Lake County government cancelled the operating agreement for the Lake County Railroad. However, instead of reviving their railroad, Lake County brought in Frontier Rail, who set up the Lake Railroad, then half a year later or so the Lake Railroad leased the line from Alturas to Perez.

As far as I know UP runs one train a week as far as Perez to interchange with the Lake Railroad. Lake Railroad runs (last I knew) one train a week on their line, going Perez-Alturas-Lakeview one day and then back to Perez the next. As far as I know there is no "plant south of Alturas" shipping anything by rail- it is true that the old SP Modoc line is still intact for a couple miles south of Alturas, but I'm only aware that it's been used for occasional car storage, and a quick tour of the line in Google Earth (imagery dated July 2012) shows a few covered hoppers and centerbeams in the Alturas yard and then nothing from there to the end of track, nor are there any connected industrial spurs. I believe the only traffic Lake Railroad hauls is originated in Lakeview and consists of outbound perlite from the old uranium plant and then lumber and woodchips from the Collins mill. Matter of fact, if you go west from Alturas in Google Earth, you will encounter a Lake Railroad train headed towards town- Lake's GP49, 12 empty chip racks, 10 covered hoppers, and 3 centerbeams.

I can't help with frequencies...sorry about that.

Jeff Moore
Elko, NV