With InDesign, colour profiles are built using linked images and created vectors, which is counter to how Illustrator and Photoshop work (where you choose a profile and the file sticks with it). This means that an Indesign file can actually (and is designed to handle) files that have both RGB and CMYK profiles. For output, the general practice is to discard one of the profiles, leaving you with either CMYK or RGB. But what happens if you discard both?
I'm honestly curious if anyone has ever output work to a printer with this. I'll update it as I get more information.