Sorry to bring old topics back from the dead, however I can add some more dirt to this conspiracy theory
My grandfather actually worked on the access block on N Hanover street as it was being constructed and also within the "NETWORK" of tunnels beneath. He was a welder.
According to him the block on N Hanover was an access elevator, that took you doen several storeys, he can't remember how deep exactly. It was connected to the dial house and GPO as you all have stated, however he claims that the tunnels went much farther than that. There were link tunnels that joined each other and formed part of a network on different levels. One tunnel was bored all the way under the catherdral street/ university areas and stopped at the Royal Infirmary, this was supposed to be a service tunnel. Another tunnel was bored all the way accross and down to Pitt Street telephone exchange.
Now the MOD have alwas said that there are six nuclear protected telephone exchanges in the UK, but have never revealed which ones, although Glasgow really is a possible candidate, and the linking of it with this tunnel network gives strength to a nuclear bunker theory. Then take into account the service tunnel from the hospital. Firstly medical supplies would spring to mind, however, the hospital is served with massive generators in case of power failure, and those could be linked into the service tunnel to provide power for something in the event of nuclear fallout.
It's all just hear say? perhaps. However this is the icing on the cake. My grandfather worked on these tunnels for many years, and was paid extremley well for it. While boring part of the tunnels under Dundas Street (next to Queen St. Station) ALL the workers were paid off and sent home. The MOD took over the contract and completed the works.
Suspicious? oh yes. If it came from anybody else I would have dismisses it as rubbish, however, I find it hard to believe that my grandfather made it all up. There IS something under dundas street/ queen street, but I guess we will never really know the truth.