The simple fact that the drive "is" removable, whether you use it that way or not, is going to be problematic.
I would highly suggest you "social engineer" the following with the IT dep't:
Have them install an internal media drive (or 4 - see various configuration recommendation threads on this forum) without encryption software. If you are not working with client's excel spreadsheets or word documents, just video that will eventually be distributed in some format anyway, (e.g., it will have a presence outside the network computers even if it is still internal), then you can make a better case for being opted out of the encryption requirement.
As a compromise, ask them to make the NLE computer's USB ports inactive except for printing. This will help satisfy the security requirements they are trying to implement. Remember, it is probably not their idea to do all this. Whatever you can do to make it difficult or impossible for data to be removed from this computer will increase your chances of making a compelling argument against encryption.
Make the IT department responsible for creating a backup of all your unencrypted media before anything else - even if they have to uninstall the encryption software, make the backup and then reinstall it. Keep this backup separate and unencrypted until the dust has settled.
If they absolutely refuse to let you be exempted, find the video "wannabe" in the IT department and involve him in the process of making the NLE software work with the encryption software. Perhaps when he gives up you'll finally be able to do without. Or, maybe, it will be working properly.
Either way, sit back and wait for the howls of dismay when suddenly some critical files in another department are no longer accessible because of a conflict between the encryption and the some security update.
That's pretty much what I expected. Apparently, it's possible to be put into a group which is exempted from the encryption requirement, so I'm currently pursuing that option. Unfortunately, I can't do much with video until this is cleared up! Anyway, I appreciate you confirming my suspicions and thank you for taking the time to post.