Any question answered...

I read somewhere (AudioKarma?) that the standard cable used by movie theatres was 12 gauge lamp cord. Apparently even over long runs like that the losses were insignificant. This may no longer be the case, and I'm not sure how they dealt with power cable issues.

Cinemas can use whatever cable routing they want, and are also likely to be running the same system at both ends, so they can pump the Signal-Noise-Ratio higher.

Or they can use a digital system with decoders and small amps in each speaker.