It's not so much that the rail itself was destroyed, but that the tunnels and stations have been closed for various reasons. Usually it's down to either a new

It's not so much that the rail itself was destroyed, but that the tunnels and stations have been closed for various reasons. Usually it's down to either a new replacement station being built, consistent signal issues, or some other passenger safety concern. Of course there have been closures due to the maintenance gap, but those aren't the bulk.