The train maker can't do anything else but to sue. If they won't sue, they are leaving themselves open for being sued by competition for unfair practices. But i

The train maker can't do anything else but to sue. If they won't sue, they are leaving themselves open for being sued by competition for unfair practices. But if they will sue the hackers and will win on some technicality (i.e. hackers can't prove that data from these units are real and not fake) then train maker can point to this case and prevent competition from suing them at the first place. It is a desperation move, but it may work. If they won't sue and win, competitors will rip them to shreds.