Trying to come up with enough other commuter lines that might use FRA-compliant DMU.

WEX in Portland? No, they have more than enough already for the busload of people that rides it.
Trinity/Dallas? No, they have more than enough FLIRTS - newer, low-floor, etc.
North Vancouver BC? Again, they have more than enough for the busload or 2 they haul.
Caltrain for daytime runs to, perhaps, Gilroy? Not likely - they have more than enough conventional train equipment that'll be surplus once the electrics start running, and Caltrain isn't high-platform.
e-BART? Now there's a possibility, if they extend toward Tracy and need more equipment to run the line; at least it would be roughly compatible with what they have now.
Orlando if ridership keeps falling? When it gets down to 1-2 busloads per train, why not run what's, in effect, buses on rails? Would need new high platforms, though.
San Diego, for Owl Service on the light rail lines shared with freight? Problem is - the light rail is all low-floor now, and the SMART DMUs are anything but. A couple of FLIRTs would be better.

Kind of running out of options here. e-BART seems the most compatible, but only if they plan to expand.