I've never had trouble gaining access to partner airlines' lounges on class of travel alone (ie when lucky enough to fly in F ). I don't see the issue here at all, because to me the oneworld blurb reads exactly that: "equivalent class of lounge." It doesn't indicate that you're only allowed to get into the lounge operated by the airline you're traveling on, it reads exactly as practised - OW F bp gets you into any OW Flounges, J bp gets you into any OW J lounges. The only extra perk derived from having Emerald status is the ability to 'upgrade' your access to a Flounge regardless of your COT.

At some airports I'd be reminded that the airline I'm traveling on operates its own lounge, but the dragons would nonetheless grant access upon presentation of a OW bp in the appropriate COT.

It is an alliance benefit I highly value, by allowing cross-use of lounges in airports where the operating carrier might not have the best lounge, eg Cathay in SIN/BKK, QF/BA in HKG, AA in LHR T3.

Agree wholeheartedly with jbalmuth - I flew AA F out of LHR earlier this year but enjoyed the use of the far superior CX FLounge with yummy noodles, snacks and Veuve. There was also hardly anyone there and for 20 minutes I was the only person around after the CX flight boarded. I hear the JL lounge is nicer but its only open when the JL flights leave, ie after midday or so.