Actually it’s a different train, the commuter train between SF and San Jose. It’s a line that’s actually full a lot of the time. Of course the diesels work fine. But Trump shares the liberal love of trains.
The new “HSR” will be using “CalTrain” tracks on the peninsula between SF and the San Jose area. This came about when the HSR became a “blended” (slow) system due to resident objections and cost.
http://www.caltrain.com/projectsplans/CaltrainModernization/BlendedSystem.html
http://www.hsr.ca.gov/docs/newsroom/fact%20sheets/Caltrain_Factsheet_Final_102715.pdf
Keep in mind that the CalTrans diesels are actually diesel/electric hybrids. The train cars move via electric motors in the wheels, nothing to do with the diesel engine. The diesel engine drives a generator providing electricity to the electric motors that propel the train. And they work just fine. Taxpayers were fed a lie, that the trains "needed" to be electrified - when they already were.