OpenRailwayMap shows a "UP Freight House Spur" extending north under the freeway near where the damage is, but it kind of peters out to the north as a tail track for a spur into the LA Times printing plant that probably doesn't operate any more.

Looking at it in Google makes it pretty clear that the spur isn't used for anything. It just hasn't been pulled up yet, or cut off and left to rot like many of the old industry tracks in that area.