Originally Posted by
asheby
Pretty sure you will be allowed it with a business class arrival. I was surely allowed in before MH joined oneworld when transiting through KUL to KCH(on economy) from a previous business sector from LHR; I was however Enrich Silver then which doesn't give you access to the lounges. I was also asked to present my previous boarding pass stub, so make sure you have it at hand!
I think this is a case of YMMV. Again pre-oneworld (last December) I came in from MEL in J, continuing on separate ticket in Y to RGN, and was not granted entry. I used priority pass instead.