Curious coincidence - I visited Vimy Ridge Memorial during the summer holidays, but unfortunately didn't get time to look into the Grange Subway there, as we were on our way elsewhere.
However, the Durand Group and Fougasse films have produced DVDs of their explorations and there's quite a lot of info out on the web as well - and on the undergound quarries of Arras which were used as barracks. A good book is "The Underground War - Vimy Ridge to Arras"
If anyone's interested I can post some links here.
Cheers
Grahami
The map is the territory - especially in chain scale.