Never happening, but even if it was wouldn't the correct charge be criminal negligence? It's not like the companies killed those people in a calculated, pre-meditated way. They're "just" externalities.
Isn't this what manslaughter is for, if you want the conviction ? I get why mens rea may not apply here, but bringing it into question may make it viable next time, which would be worthy (or likely I don't understand law well enough).
I'm not a lawyer, first of all! I'm not very knowledgeable either.
Mens rea, as far as I understand it, definitely doesn't apply here. Bringing it into question undermines the case if you're trying to build a conviction around it. Better to have a wide variety of provable smaller claims than one big ticket item you're doomed to fail, as far as I understand it.