I've only been somewhat in the area of it when working once. As in one of the quotes above, it makes a very loud bang when it operates.
I was not inclined to go closer even if there wasn't an exclusion zone!
The break is like the rail was snapped rather than cut.
This is very different to the relatively slow hydraulic cutting tools used by the fire and rescue services (saw them practicing lots of times because I used to live near a fire station as a child).
I'm guessing it bangs is because it's not being cut but sheared (ie the blades of the shears are not sharp, it's actually the force of the 2 shears moving against each other which is shearing the metal in to), plus the high tensile nature of the steel will also come into play.
As an engineer I've heard 6mm mild steel plate bang when being cut on a guillotine with blunt blades and a incorrect cutting angle(/rake) applied.
And yes it would be different to a fire stations "jaws of life", I've operated a hand operated set of them (which operated in the 100's of psi, the shears your talking about typically work in the 1000's of psi, which makes one hell of a lot of difference in speed and force applied).
Btw, cutting and shearing are 2 different things, so yes the end wouldn't look like it's cut. Typically the end wouldn't be square (90°) and probably curves off slightly to the rest of the metal, similar to a length of bright mild steel flat bar when bought new from a steel stockists.
Getting back on topic... in years gone buy a reasonable amount of rail had been repurposed for use as part of a safety fence at banger racing tracks, although this has fell out of favour more recently for armco or boiler plate.