Join Date: Oct 2006
Location: London, UK
Programs: BA Gold, VS Silver, SQ Silver, IHG Plat Amb, Hilton Gold, Marriott Plat, Accor Silver, Radisson Prem
Posts: 16,871
Assuming China Eastern is in the same terminal as oneworld flights, then yes you can use the Qantas/BA business class lounge, as it is joint-branded.
You wouldn't be able to use the CX lounges.