I don't understand why this topic rolls on and on. 4-engined jets have operated across the Atlantic for decades, and SOPs have equally always been in place, and are known to all concerned. There must have been many engine failures before starting the transocean crossing in that time. Did they all turn back ? Was this BA flight the first one ever that carried on ?
LAX to Europe does not actually do too many hours over the ocean, it is probably one of the lesser ETOPS-demanding routes, not like a transpacific flight.