Another thing to think of: most transit rail cars that I've seen specs for call out accel and decel rates, not the specific types of brakes. Light rail cars seem to cluster around 3-4 mph/s accel and 4-6 mph/s maximum braking. Heavier electrics, especially those used on freight lines, tend to be slower at both accel and braking. To meet the specs for light rail, of course, normally requires a combination of dynamic/regen, friction, and track braking.

Personal experience on light rail cars under emergency braking is that you wish for a seat belt but don't really need one (until you hit something big, which in my cases didn't happen). I tend to ride facing backward so unusually strong braking doesn't try to throw me out of the seat - some drivers aren't good at keeping passengers comfortable. Having also been on conventional passenger trains that went into emergency, it's clear that light rail can stop MUCH more quickly than a normal train from similar speeds.

My comment on the light rail appearance of the Italian wreck was based only on the photos. Agree that at a combined impact speed of 200km/hr no equipment is likely to perform well. And one reason for the CEM push in modern stuff is recognition of more aspects of crashes than just crush failure. Simply building a stronger tube transfers more force to the occupants, so even when meeting FRA standards CEM is necessary in modern cars.