You asked about the Sprinter and freight activity. When North Country Transit District re-constructed the Escondido end of the line (3 customers - chicken feed manufacturer,lumber wholeseller, and an irrigation pipe/sprinkler head manufacturer), a long run-around track was built next to the main line. A RailAmerica SW1500 was used to do the switching in this area. Now I do not know if RailAmerica leased the switcher or is under contract to do the switching.
BNSF bring up the train from Oceanside usually three time a week, drops of the cars (10 to 20 - mostly covered hoppers and flats with lumber) on the run-around track and then goes back to Oceanside (connection with the San Diego Northern Railroad/North County Transit District. The train usually arrives between 11PM to 1AM. The RailAmerica will switch the dropped of cars during the week at night after 10PM.

This was the routine uptil 3 months ago, and I would think it still is the process.