ViolentPanda
Hardly getting over it.
There aren't, assuming an average cross section of 6ft (a tunnel big enough to walk through) gives the tunnels a total floor area of 757 square miles somewhat larger than Greater London's 600ish square mile area. Either this 2 million is wrong (2,000 is very believable) or that 2 million miles includes things like cabling ducts a few centimetres square which might be a tad difficult to cycle or walk through.
You're just being defeatist! Once Gauleiter Gammons perfects his shrinking ray, we'll all be able to use the cable ducts as mass transit!