They certainly do, as was evidenced when the Silbury Hill tunnel was reopened back in 2007 for the conservation work - there is apparently still loads of metal inside which cannot be removed.
I think some of the people mentioned in your article made and appearence in the recent tv programme "Monty Halls' Great Hebridean Escape" and although I didn't catch the whole series I know part of Monty Halls remit was to open up walking/archaeology trails. Very interesting, thanks Drew.