I'm not sure which lounge LY contracts at EWR, perhaps it is still the BA lounge. If it isnt I dont think you will be able to enter the BA lounge with your AA status because you are not actually flying AA metal, and El Al is not part of Oneworld. Lounge access with AA Platinum status only works if you are flying a OW carrier, codeshares are not considered to be that if the actual carrier is not OW.