Hah!
In honesty, I did try having a look, but I can't find the report that would tell me.
I imagine it's about 9-12 months for either a hellish deDACS conversion or as fault that's never going to get fixed (such as a speed complaint on a long line).
For the record, the longest provision that I've had to deal with was 13 months, which invvolved BT digging up a motorway and laying down 40km of cabling.
Edited by deleted (Thu 22-Nov-07 16:04:15)