The microwave horns are incredibly, incredibly tightly focused, though. (That's why they made 'em so big.) If you're not literally between the two ends of the link, you're not getting significant energy. And if the beam actually touched the hill, it'd diffract badly and spoil the signal.

Also I don't think any of those are still active, are they? Most of 'em that I've seen have the feed waveguides removed where they get near the ground. I always thought it'd be fun to make an adapter/coupler and stick a wifi card onto one of 'em because 2400Mc is within their passband, but I can't find a pair pointing at each other where both ends still exist.