After Hurricane Katrina hit, BellSouth announced that it would take 3 months to restore phone lines. Volunteers using WiFi gear were able to connect churches and community centers within the first weeks and within three days of setting up an asterisk call server, routed 10,000 phone calls. Reliable backup infrastructure can be brought up in hours or minutes if you are prepared and have a plan in place.
(If you haven’t checked out the Instructables site that this plan is posted on, I reccomend giving it a spin. It’s a great and inspiring resource for DIY folks).