Very sensible posts.
The current line will be repaired and in due course better defenses put in place. That will be all. No new lines, unless the government comes up with more cash and pays for the route entirely. NR sure as hell dont have the money after the CP5 settlement has been worked out!
The current line, no doubt with degraded working, will be repaired and reopened ASAP.
Well, it would certainly be a wasted opportunity if when the dust settles, the opportunity to improve transport in the region isn't taken. I hope the locals turn the screw on their marginal MP's and Councillors and force something to happen.
With regard to costs, I suppose you can only really look at the comparable projects that have taken place in Scotland.