Looking at some possibilities for an upcoming trip and I noticed that if I book Premium Economy and one of the segments has no PE, then one will be put in Business class (Z). It used to be that segment would be booked as Economy (B). It's nice because it could save a few upgrade certificates. E.g., last year I flew YEG-YVR-HKG in Premium Economy with the domestic segment downgraded to Economy. Don't know if this was announced, but if it was I missed it.