Shore Guy;
As to EGPWS warnings, if not a direct GPS feed to unit, and appropriate software/terrain database installed, close to the airport, protections are disabled to virtual GPWS status due to lack of confidence in position (even if FMS has a GPS input). All EGPWS manufacturers, Boeing, Airbus, and regulatory authorities STRONGLY recommend direct GPS input to EGPWS.
Yes, that is my understanding of both the requirements and the outcomes, as provided on the Honeywell website if I recall.
Our manuals do not fully provide that information so crews will not know whether their EGPWS is connected directly to the GPS or what it means to EGPWS accuracy if it isn't connected. Many of our a/c do not have GPS. Where some information is mentioned, (different chapters, depending on the airplane type), it is anything but clear whether the connection is "direct", or is "GPS", but through the FMC.
Whether El Al's installation takes GPS information or uses FMGC information (even given what you say), I cannot state.