Picked this up on the Sveasoft forum
we have several hundred APs connected wirelessly covering an entire city with a seamless mobile network. These are all on the same SSID (non routed) and we can seamlessly roam everywhere up to about 55mph. We can do mobile VoIP with only a slight delay as the handoffs occur, but no calls are dropped.
more info on the city we covered is here: otawawireless