The Network Rail report also states that Meldon Viaduct would need replacing. This again depends on what option may be used to cross it, or build a new viaduct. I have been told that the Meldon Viaduct company think it could be repaired for around £15-£20million for a single line of track. This is much cheaper than a new viaduct. This could make a significant difference to costs.
The reports figures also include the inevitable 66% contingency on top, or optimism bias as you state Grahame
Every re-instatement is going to have its special case expensive sections. Option 4 (alternative route B) from the Network Rail report quotes £470 million for a line from Newton Abbot to Exeter via Heathfield and Christow, which is about 5 miles of just operational line and 15 miles of reinstatement. At £20 million per mile (re-instated) and £14 million per mile (upgraded) that comes in at
£370 million - you need to go up to figures like £25 million per mile for re-instatement and £19 million per mile for upgrade to reach the
NR» quoted £470 million.
Agreed I'm including contingency. Also noting the report is dated September 2014. Have prices gone up since then, or would improving techniques allow savings to be made?