I´ve so far only stumbled upon the term "cab car", as well in documentation of some METRA, AMTRAK, Caltrain, Coaster, and Metrolink models for MSTS / ORTS, as in one or the other documentary found on Youtube.
Anyway, we got native English (British or American) speakers here, so why not ask them? :wtf01:
Cheers, Markus