microwaves go about 10% further than the horizon, barring any tropospheric ducting - which cell towers shouldn't, in general.
The issue you have with long distances is multipath, which can throw off the complex timing required to have multiple users in realtime on a single radio.
I've heard that US spy satellites used to eavesdrop on soviet telephone calls transmitted between line-of-sight ground-based microwave relay towers. The relay towers used directional microwave antenna aimed at each other, but satellites in space could pick up those signals.
The issue you have with long distances is multipath, which can throw off the complex timing required to have multiple users in realtime on a single radio.