VV,
Networked sims do work and can be, and indeed are, networked worldwide via broadband - ask the yanks.
Thats because the Yanks have the same aircraft types splattered all over the US and in many ways they HAVE to network their synthetic training devices.
We however tend to put all of our eggs in one basket. Lynx at Yeovilton, Merlin in Cornwall, Chinook in Hampshire.
Trust me, I have looked long and hard at this and indeed conducted an extensive study into how the MSHATF works and in particular how the TCC operates. The wide area network facility works but the big question which was never answered during the writing of my paper was..... Why? Why spend millions networking simulators together when it is far, far cheaper to (and more importantly provides better training).... simulate.