City wide wifi is hard. you can cover a street or a couple of streets or even a CBD area outdoors, but trying to blanket an entire town/city is hard. The physics of WiFi technology works against you. This is assuming you want everyone to access their wifi with smartphones etc - without a CPE device.
The reason it works in some areas e.g. Google-town is because their houses are made of "cardboard" and their WiFi regulation allows for 10x more power than ETSI regulations used in Europe and Kenya.
If you're looking to give everyone a CPE device on their roof or in their window & are happy with providing smartphone coverage outdoors at street level - now that's a different story. Check out the model for Mawingu NetworksÂ
http://www.mawingunetworks.com. There are also a number of similar operators doing this e.g. Haggai with Unwired and others.
Wifi works great for hotspots - not so great to "blanket a city"
R