You are extremely lucky to live where you do, Feather River Canyon out of Oroville is right next to you. One of the most scenic routes there is!
See these links below:
As far as knowing WHEN a train will come, that is a LOT harder. In reading up on the FRC - it looks like it averages 20 trains in a 24 hour period.
You MIGHT try going by the old Yard in Oroville - it looks like UP maintains a track maint facility there:
May be friendly, may not. If you walk in and just let them know you are a photog and you are interested in shooting train up in the canyon - they may be willing to let you know how many trains will be running that day and when. May not be friendly, you just never know.
Definitely get a scanner, the freqs are all over the internet. Also if they have signals in the canyon you can learn to read those. If they are red, there is a train in the block. Yellow or green a train is in the block and headed to you. Scanner can pick up the defect detectors, EOT devices etc and crew traffic. If you can hear the EOT squelch a train is really close.
On a line like the FRC - it may be busier during the week vs weekend too.
If you see ANYONE else there taking photos - stop and talk to them - they may know a lot about it.
Also look and see if there is a local train/hobby shop near you. They would def have good ideas on how/when/where to railfan.
Lastly, I just ound these links. It looks like there is a NORCAL railfan group on Facebook
That may just be a GOLDMINE for you!
Good luck man! I am jealous you live next to the FRC!!!!!! So jealous! My best option is the BNSF transcon 2.5 hours awayand its full of ugly green and orange pumkins!
I would like to add, that the major RR's no longer run on time tables - they just run when they have a load + crew + open track lol. The only real regular trains now a days are major unit trains of say coal, grain or intermodal, and only the guarenteed trains are on a really regular schedule (usually transcon runs with guarenteed run times like BNSF LA to CHI thats a 48 hour guarentee). Other wise they run in the CTC blocks as long as the crew has time lol!