What sort of emergency are you planning for that would take out both POTS (dial up 56K), GSM/EDGE (850, 900, 1800, 1900 MHz), UMTS/HSDPA (850, 1900, 2100 MHz), T1, DSL, ADSL (2,2+) for your required data connectivity but not also take out another network such as HAM packet radio data (if available) or even your own network constructed using the fixed non LOS wireless Ethernet connections etc.

You will still need a gateway to the Internet for Internet access, where on the periphery of the comms blackout would you expect the gateway to be located?.

Do you have Satellite Broadband services where you are located to act as the gateway for your private WWAN.

Constructing your own emergency wireless network (combination of Routers, Wireless Ethernet, Satellite Broadband Gateway, and local Wifi would be expensive (the Power Supply requirements i.e. Solar Battery, Gen sets etc, create the additional expense) but again what makes you think that your own network would be anymore resilient than commercial providers except from the point of view of data communications congestion assuming of course that commercial networks either fixed cable, POTS, Wireless 2,3G are available in your area.

Chances are if all the above commercial communication network providers go down, you are basically left with the Post Office, carrier pigeons, runners and the odd HAM running his valve set talking into his mike saying 'Mayday, Mayday, Is there any one out there, over'.

BTW if you do end up creating your own emergency network, the old fashioned red rotary dial telephone on your VOIP network will add a little style and help justify the cost.