I attempted to ride it in July 2017. It's about 10-20% rideable, unless you have a fat bike and a machete/chainsaw. A lot of it is right next to highway, so you get all the noise of highway without the benefit of pavement.
The only worthwhile parts are the first 10 km, the last 10 km, and the 10 km in and on either side of Paris. That's it.