I have reviewed this document on behalf of the Operations and management directorate.  As a disclaimer one of the authors is a coworker,  however as the authors employers collectively represent a significant chunk of the CDN industry and as I also work at a CDN that would likely be the case under other circumstances.

This document appears to be ready. It's appears to be broadly consistent with how these headers are interpreted by CDNs today and by providing some useful clarity as to how they should be interpreted better interoperability respecting origins / clients using multiple cdns can be achieved.