Last I knew the NJT monitors did show the Amtrak departures right along with the NJT departures. The train numbers start with an A and the destinations are typically not places served by NJT and they show up in a yellow colored bar. At the worst, one could stand at the bottom of the stairs and look up to the upper level and still see the Solaria board too.
However, one can also monitor Amtrak's departure via the NJT
Departure Vision website. The track numbers still show up at that website, I just checked, right along with the NJT train track numbers. And last I knew, Departure Vision took it's info right from the PSCC info that shows on the NJT monitors.