I didn't really get your question. So, you want to have two T1 connections set: one for the Media and one for the tv production. I wonder why you want this. Why not share one T1 connection to both?
Anyway, now you are wondering, if you can use a lan and a wan (=T1) at the same time. If you have two network plugs or you are using airport connections, it's no problem.
But I think you will need to tell more about your network settings. How many computers are there, how would you plug the network to the wan (router or directly plug it to one of your macs and share the connection).
Ahhh, slowly but surely I am understanding the problem. You want the whole thing to be in one subnet (lan) but use two routers or routing macs at the same time. I think a vpn server would do it fine. You can have two vpn servers for your two T1 connections and everything that is going to the lan won't be directed to the vpn servers. Is that what you meant?