The drawback with microwave is low bandwidth. To get around that, their solution would rely on the microwave network between cities for web and data traffic for which minimal latency is important. Other things for which latency isn’t as critical, like video consumption (which is currently 78% of web traffic), could continue to use existing infrastructure, so congestion wouldn’t be an issue. Traditional fiber would be used to bring data to users up to 100km away from the microwave endpoints; even at that distance, the latency introduced by fiber would be minimal.

Source: How microwaves could help you surf the Internet at the speed of light | ITworld