This week I (humble Platinum) flew from Paris to Bari with Alitalia on a Business Class ticket. With a 90 minute transfer in Venice a colleague (F+ Red) and I went to the Alitalia lounge and were bluntly refused access. The reason: the connecting flight was a code share and was not on Alitalia Metal (even though it was an Alitalia flight number) so Flying Blue did not give me access and as it was a single class plane, business class did not let me into the, extremely empty, lounge.
We both called Flying Blue who actually answered and were friendly and they spoke to the Lounge attendant with our mobile phones - but she wouldn't change her (small) mind saying: "It was a decision of the AF station manager not to let FB Platinum members in when Flying with a Skyteam ticket on flights not actually operated by the ST partner."

Flying Blue then confirmed over the phone that this was indeed a new rule: Skyteam Ticket, Skyteam Flight Number, Business Class Fare is not enough: if the flight is operated by somebody else - no lounge access.

I can't find this on any website - has this happened to anyone else?