Here's what I imagine they'll be doing: (1.) A Surfliner train coming down from Glendale will use the tracks on the east side of the river and at 9th St. Jct. proceed as if it was going down the Alameda Corridor like a UP freight train would do. (2.) When it gets over by the J Yard and beyond the applicable Control Point, it will reverse direction (easy to do with a push-pull train) and proceed on the route that BNSF freight trains use when they're coming off the Alameda Corridor and are headed for Fullerton.