Yeah, I am quite certain that Metra will never run a really frequent suburban service. They are too oriented towards generally infrequent and big trains, and any travel pattern that does not fit such, they don't want to have anything to do with. So I tend to agree with what MetraUPWest says. Unless there is a complete change in service philosophy at Metra they will not know what to do with DMUs effectively.
OTOH, and outfit like LIRR may actually be able to make really good use of them for outer zone service, even making more service to Greenport and more frequent Patchogue - Speonk or Montauk turns more feasible. Even Port Jeff could do with some filler service covering huge gaps at various times of the day, though they will probably need to start using those passing tracks in off peak hours, other than the Smithtown one.
NJT could make good use of them on Long Branch - Bay Head, or even on the Boonton Line and beyond Dover during off peak, thus making Mt. Arlington and Rt 23 more useful stations, but I am not holding my breath