Surely high speed trains suffer from network wide monitoring outages too? I would imagine they're susceptable to similar issues.
Sure, but having a _second_ way to get places can only help.
still, it would be nice to have an alternative as a backup.
But likely not at the same time as the planes.
Yes - see German trains going down for that reason a few months back:
https://www.reddit.com/r/germany/comments/1udup2j/trains_hal...