I found a rather extensive write up about this on an urban exploration site a year or so ago, but I am not sure if it was the same people.
From what I read, the guys were no bullshit. Getting into the tunnel involved sneaking past some guards (not really dangerous but still a bit risky), forcing or picking a lock or two, then setting anchor points and a vertical descent by rope into the tunnel.
I found a rather extensive write up about this on an urban exploration site a year or so ago, but I am not sure if it was the same people.
From what I read, the guys were no bullshit. Getting into the tunnel involved sneaking past some guards (not really dangerous but still a bit risky), forcing or picking a lock or two, then setting anchor points and a vertical descent by rope into the tunnel.