The Argentinean government is placing a $506 million order for 409 new electric multiple unit passenger cars to be built in China by the China South Locomotive and Rolling Stock Corp.
You can use the methodology for environmental regs that weighs the cost against the benefit and see if the FRA stds as they exist are worth their cost.
Elsewhere in the world the so called “loading gauge” is much a lot less allowing for higher speeds and lower fuel costs. It is done with investment in infrastructure and avoidance signal and operating systems. Cost less and seem to be effective in economy and safety. Will the US ever use it? I would say yes if it were to be on dedicated passenger track except that subways on such dedicated track here are heavy.