This is also mentioned in Metro 2033 by Dmitry Glukhovsky - http://en.wikipedia.org/wiki/Metro_2033_(book) Amazing science fiction book.

Same under Beijing. There is a parking done in an old military zone, the doors are 50cm thick and the height seem to allow tanks go. Its is said there are many such tunnels under. They feared Russians, in fact. I wonder why they don't open them to cars or build the subway there.