There are some Union Pacific freight trains that run on the Saugas Line, mostly during the overnight hours. Metrolink runs about 20 trains a day between Lancaster, CA and Los Angeles, CA. Every so often the Saugas Local runs between Burbank Junction (where the Saugas Line and Coast Line split apart) northbound to Saugas, CA.
Union Pacific has about 15 trains a day that operates over Tehachapi, most of the traffic is to/from West Colton. There is joint traffic between BNSF and UP between Mojave and Kern Junction (Bakersfield). In a 24 hour period between both roads there are about 30 trains.
I think it's running 2 or 3 to 1 in favor of going to West Colton.
Most of the UP traffic bound for Los Angeles and or Long Beach operates on the Coast Line between Oakland and Los Angeles/Long Beach and one or two to West Colton. There are 8 - 10 Freight trains (all UP) that run along the Coast Line every day. The "oil cans" have one train in each direction between Wunpost and Long Beach, one quality merchandise train in each direction between Roseville and Long Beach, one manifest train in each direction between West Colton and Portland, OR with the rest of the traffic being intermodal on the Coast Line evry day.
The Saugas Line travels on the north edge of Bob Hope (Burbank) Airport with the Coast Line on the South edge of Bob Hope Airport.
There is some intermodal traffic on the Saugas Line, but it usually runs during the night hours.
BNSF runs double stack trains on the Tehachapi Line. This is traffic between Richmond, California and Barstow, California. BNSF runs their trains during the day and there is some UP traffic to/from West Colton during the day light hours as well.
The UP traffic between Bakersfield and West Colton sees action over Cajon Pass and Tehachapi.