Job,
Still no answers. I don't know why it seems I am always pitching for KDN but hey....
I believe that on a 3.5 wimax you would be able to get a signal from NSSF & if that doesn't work there is always a BTS @ Athi River or Kitengela.
From past experience, there was link just before mlolongo behind astrol to the NSSF BTS.
But if you are not willing to put up a mast, then pole.
I have not have answered your original query of the point to point solution, i.e I don't know anyone who is selling this connectivity in the area but HTHs.
All the best.
Regards,
--
Lusiola Brian
Everyone has photographic memory, not everyone has film though.