Has a railroad preservation group ever restored a tunnel that was closed, sealed off, partly filled in, or partly collapsed?
It would be very, very interesting indeed if the Alpine Tunnel (1800 feet) at the Continental Divide in Colorado was reopened. It is currently sealed off at both ends.
I believe some mining engineers and miners could do the job fairly easily.
"The tunnel was abandoned in 1910 by the Colorado & Southern due to minor damage in the interior."
"The east portal of the tunnel has collapsed and the west portal has been covered by landslides."
https://en.wikipedia.org/wiki/Alpine_Tunnel
Might there still be tracks inside?