[John Jorsett]

It would be interesting to get some additional details, like how one monitors Germans while sealed in a cave. Electronic listening post perhaps? Periscopes?

[Stoat]

It would be interesting to get some additional details, like how one monitors Germans while sealed in a cave.

Agreed.  Hopefully the survivor whose story this short article is based upon will be willing to provide more details.  It's such a compelling story, this short article mainly serves to make the reader wish for more.

 Electronic listening post perhaps? Periscopes?

Probably both, and everything that was technologically available at the time.  They had years available to set up the facility, so it was most likely planned quite thoroughly.

[Stoat]

Another item that will likely be of interest to readers of this thread:

Dedication of New Normandy American Cemetery Visitor Center Set for June 6, 2007

[conservative in nyc]

There are man-made caves inside the Rock that have been built to defend Gibraltar from Spanish attacks. Those caves have openings large enough to stick a cannon out of. See the pictures on this website, for example.

All the soldiers would have to do is hide in those caves (or even more secret caves that the public doesn't know about, which could have even smaller, less detectable openings). They would provide a lookout from above the city, and wouldn't be easy to detect. Remember - the Rock is about 1,400 feet high. Thus, a cave can be well below the top of the Rock but still above much of ground below. The plan makes sense to me. It would have used the local geography to the Allies' advantage.