CO has some attractive fares from Philadelphia via EWR, where the PHL-EWR leg is actually an Amtrak train from ZFV (Phila. 30th St) to the EWR train station. As often happens in the screwy world of airline fares, the connection is cheaper than originating at EWR.

One of my relatives is thinking of taking one of these. She lives near Trenton, so could she take the train from there? It appears that the CO train segment is turned into an Amtrak ticket that you pick up at an Amtrak quik-trak machine, so would it work if she picked up her ticket in Trenton? The conductor onboard doesn't care so long as you have a valid ticket when they check you, but would Amtrak or CO's computer get upset if she picked up her Philadelphia ticket at a machine in the Trenton station?