I have two copies of iTunes that I have authorised to the same Apple ID. I use one as a server and it has all our digital copies of movies. I have another that I only use for Syncronisation (i.e. no more that 64GB of content on it). I'm currently putting the digital copy that I want on the iPad into the second iTunes instance and redeeming the code again, I was wondering if I can just copy it from the other iTunes across the LAN?

This is more important for digital copies that are not actually on optical media and head off to the cloud to download it all over again.