I heard that KLM will keep lounge access for PE's irrespective of airline flown at their OWN lounges only, i.e. AMS, JNB, DXB and a few others.
For other lounges not owned by KLM, PE's will have to be on a Skyteam flight in order to get access. As far as I know that's the Skyteam Elite-Plus standard. Policy for GE (also Skyteam Elite-plus) remains as is: you have to be on a Skyteam flight to get access to lounge, also for KL owned lounges. For SE (=Skyteam elite) no lounge access unless Business class ticket.

Dare I ask...how does this compare with Star Alliance and OneWorld? Do highest tier members have lounge access irrespective of airline flown?