Bumping this thread to share my recent experience, traveling as a FB Platinum CDG-LAX on AF then LAX-YVR on an AF-marketed WS-operated flight.

- Lounge access: I could access the Delta SkyClub at LAX (funny thing is that I asked DL via twitter beforehands who told me I was not eligible to lounge access as my flight was operated by Westjet, but decided to try my luck at the airport and... it worked!),
- Checked luggage: I was traveling on a Light fare. Booking told me I had no checked luggage on the outbound leg (although STE+). Same at the airport self-service kiosks where I was asked 50€ if I would like to check a bag. As I was travelling HBO, I don't know if that was only a bug (and an agent could have waived the fee) or if it was due to the WS-operated flight,
- Skypriority: could access at LAX the Skypriority lane at security with my AF BP printed in CDG, but not at boarding on the WS flight (they had reprinted a BP for me and I was zone 3),
- OLCI : I have been automatically checked in by AF on the WS flight. Could not choose my seat in advance though, but was assigned in a window seat at front (seat 5F). Don't know if it is just luck or a kind of status recognition,
- On board: classic WS service (free drink/cookies + BoB available).