Large Dense DigiMesh Network

I have an application which would theoretically suit say 500 XBee Pro units running a DigiMesh network, all within a bounded area say 3km in diameter. I need to get small amounts of data from any of the 500 points, which may be moving, to a base station on one perimeter. Any of the 500 units can transmit asynchronously every 10 minutes. Has anyone ever had experience of putting more than a few such nodes into a network? Because all the nodes will be moving the network needs to be self healing and adapt continually. Thanks for any advice you can give me - Robyn