The Italian wreck looked like a couple of light-rail trains hitting each other head-on at track speed. Light rail cars (transit cars in general) have nothing near the strength of mainline rail - which is why it can't share tracks with it. Remember what the wreckage looked like in DC in that Metro rear-ender several years back?

A properly engineered "crash energy management" scheme can substitute for part of the FRA strength requirement if the necessary exemptions are obtained. It's difficult to obtain them due to the amount of analysis and testing needed, but it has been done in some cases. Of course, the one-off engineering leads to construction and compliance problems as the new cars for IL, CA, etc demonstrate. One-off ANYTHING tends to be costly and less-than reliable - ask the Air Force what happens to unit cost when they decide to cut the purchase numbers after a plane goes over budget - the research and engineering (and political cost-padding) still has to be paid for.

Frankly, between the strength and CEM requirements, I think we have more crashworthy passenger equipment in general than most other countries do. That's especially necessary when considering what our freight trains weigh; you really don't want to hit one even with FRA-compliant passenger equipment. European freight trains are much closer to their passenger trains in mass and operating characteristics than ours are. OTOH, as the article pointed out, the extra weight does affect performance in general, including crash avoidance. If PTC were universal and effective (neither of which will be true with the current rollout in the U.S.) then yes, it might be possible to reduce the crash requirements somewhat. Though trains will still hit trucks at grade crossings even if all train vs. train collisions are eliminated. Pretty much like Minis vs. SUVs - both meet the "standards" but the crashes involved in testing pretty much compare like to like, not the different weight classes.