Put a medium-sized antenna mast in every neighborhood with a few hundred highly-directional antennae pointing a clusters of 4-16 houses and put highly-directional rooftop antennae on each roof, and you can re-use the spectrum many times over.
Serve these neighborhood antennae with fibre if you can or highly-directional wireless if you can't.
The issues under this system will be that it's a whole new infrastructure including antenna sites, you will need to pick radio frequencies that are largely unaffected by weather and which don't compete with existing frequencies, etc. etc.
But assuming a weather-resistant block of frequencies that can feed lots of bandwidth to dozens of users at once is available, you won't have a frequency-allocation problem.
Another solution, one that may be more practical, is to just chuck the whole wire-to-the-home infrastructure and beef up the cell phone system so everyone can feed their home internet via cellular. Heck, in areas where the cellular network is already robust customers can simply "vote with their feet" now and cancel their land-line service entirely. You guys do have "number portability," don't you? If not, you should. It's nice.