.....any navigational system the crew were looking at would surely have shown them the way to their real destination.
Hence the curiosity about the deviation. Much depends on crew techniques and SOP's. I've seen it where PF says, "can you see the runway yet?" The crew is visual with the ground and flying on automatics for the approach. Both pairs of eyes are then focused outside the window: one calls, "I think it's over there." PF confirms he has a runway in sight, disconnects and aims at the new target. Human behaviour, rather than system malfunction.
It has happened where a/c have landed at the wrong airport, even with a MAP. The real target runway showed large deviation from the a/c symbol while on finals for the wrong runway. Only picked up if someone is managing the office inside.
There is a Glideslope aural/visual warning. The lateral & vertical deviation is displayed on the FMC, silently. Someone has to monitor it. Are we going to introduce another aural warning to alert crews they are not doing their basic job?
I'm not saying any of this was the case here, hence our curiosity why a crew would disconnect an automatic approach so early on a bad vis approach without being certain of the visual reference. The geographical position is quite different, and I suspect the approach lighting is also, and the relevant DME from touchdown would have given a clue as well.
Remember the AC A320 crash in Halifax where there was no SOP to monitor DME inside the FAF. Similarity here? Situational awareness? It is such an odd action from a professional crew on a grand new a/c that the management needs to know the full story. It is not to be dismissed as a non-event. As with AC A320 event it could lead to altering SOP's.