As I understand it, it's a bit like the TET (Trans European Trail) for trail bikes - put together a set of routes, which can be used to travel across the country on known good lanes etc. (they are apparently trying to like the southern ones to the northern ones, so you can ride the full length from Cornwall or the home counties up to Scotland). So you can download the GPX, modify it to suite, and use it as the basis of exploring an area you don't know. There is a guide book for this, but not sure it really needs signs going up.
Certainly TET is a living thing - the route can be constantly tweaked depending upon what the linesmen in each area know, so you download the current version before starting out.
I've ridden parts of TET and discovered areas I'd never ridden, I'll probably ride parts of this in a similar vein - likely with MrsH.
It's also good publicity - mainstream coverage of the sort of things you can do, encouraging riders who hadn't considered it to do more and have adventures.