With the new track construction at union station, and with the help of the railroaders and hard core railfans who write Wikipedia articles, it has been possible to identify components of the remote systems that regulate passenger trains. I'm sure that our Anonymous Amtrak reader, or others more knowledgeable, will correct my mistakes.
As trains leave LA Union Station, they pass a box with a light that says "CTC begins". I believe CTC stands for Centralized Traffic Control, which essentially means there is a dispatcher who functions like an air traffic controller to regulate signals and switches remotely. This ensures the smooth running of trains particularly through regions of single track, without relying on the train crews or local towers to keep track of the traffic individually to manage the switches.
I assume that the blue structures bolted onto the new tracks at LAUS are magnets associated with the CTC, since they are right next to the light box.
Or are they part of the Automatic Train Stop system? That is required on passenger trains in certain regions to allow them to go as fast as 90miles an hour. It works via a magnetic shoe on the front right of the locomotive (or cab car) to pick up a remote signal. This conveys a signal d to the engineer who has 8 seconds to acknowledge that he got it, before the brakes automatically deploy.
You can see the shoe in the picture to the right--it is the lowest structure you see, hanging off the truck to run at the outside of the track.
Apparently this is found in only parts of Amtrak's service area, including the Pacific Surfliners. So, any locomotives from elsewhere in the system that "sub in" for the PacSurfliner engines, have to be fitted with this shoe. The long distance locomotives from the Southwest Chief also have ATS shoes, so that's probably where our "Gennies" come from.
This is what comes of walking up and down the platform while waiting to board the train, and noticing odd things on tracks and engines.
Update: our friend Anonymous in the comments says that the blue bits are
insulated joints. The signal system functions via low-voltage electrical currents which run through the rails, each "block" of track is independent, so at each signal the tracks need to be segregated electrically to differentiate the blocks in the computer.Otherwise, he says this is pretty accurate. Praise from the Pro is praise indeed! :-)