I've been using OSC transmitters/receivers for something similar - except sending the data over the internet between two theatres. The patch is essentially a multi-channel vision mixer with virtual PTZ controls and a cue recall system, and all of the control can be operated either locally or remotely. There's also a couple extra computers in one location with a different patch to run live subtitling (also via OSC). I imagine you could do the same with Net Broadcasters and a VPN - OSC is just a little more convenient, because you can point it directly to the other computer's public IP address.

Running Isadora on multiple machines is great. Especially with NDI and TCPsyphon to send video around as well as controls. I hope the licensing changes make it a little easier to deal with, but it's a great feature either way.