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terrestrial microwave engineer here: "80 GHz" is actually 71-86 GHz FDD. The original FCC band plan allowed for 5000 MHz wide channels each direction and basically OOK or BPSK level modulation. Newer radios use 250, 500 or 1000 MHZ wide FDD channels and QPSK or better. Incredibly wide channels can be used because it falls off in the atmosphere so rapidly after a few km, and the antennas are all very narrow parabolic reflectors with less than 1 degre beamwidth.

Basically no colocation interference issues are possible unless two companies try to shoot from the same rooftop, to also the same rooftop, using the same channel AND the same linear polarity.

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Thanks for jumping in! Sounds like it's really nice for urban small-cell deployments, campus networks, etc. Do you experience a lot of issues with keeping links aligned at those tiny beamwidths?

Not really, 80 GHz is definitely difficult to aim, the very center of the beam is quite small. The mounts for the most popular antennas accommodate this and have very fine adjustments for the azimuth and elevation. Keeping them aligned long term? Not a problem as long as the mounts the radios are on (whether non penetrating or bolted to a wall/structure on a building roof) are done properly.

I'm wondering how the natural motion of some taller buildings affects this kind of deployment.

Lots of buildings swing and twist in the normal course of the day. We found this out with some of the free space optical solutions available.

It can have some effect but at the distances aimed (max 3km for a high reliability, high Tx power 80 GHz link) it doesn't affect much. A link that is a nominal -34 RSL on a clear sunny day might drop to -36.5 as a result of building sway (such as if one end is on top of a 60 floor tower). Weather is the main issue not heat expansion/contraction or sway.