At least in the Military sphere it's been possible for a number of years now. I'm aware of a large number of exercises involving multiple simulations integrated into a bi-directional environment.
The Combined Arms addon is a great addition to the DCS series but say you wanted to have a human SOF team hitting a target and A-10s in support/ then also have some tankies as QRF...each group in their own simulator but able to interact with each other.