I delivered a Cessna 210 across the pond to Holland - 8.9 hours non-stop from Gander to Shannon. All you have to do is disconnect the overwater sensor and the plane thinks it's over land the whole way.
As for the Airbus, or any other transport category plane, I think you're talking about the required equipment for ETOPS. The MEL allows equipment to be inoperable, but many of those deferrable items are required for ETOPS operations.