Is there any senario however remote when the cross feed pipe could be needed in flight, even if it is a million to one chance of it happening ?
None that we can anticipate as realistic.
The Staneval has looked at the various scenarios that might need the use of a supplementary air conditioning system (ie open the crossfeed pipe), but there are no such scenarios that do not require multiple, unrelated, in flight system failures. Therefore, the SCP valve is now being replaced by a solid metal bar running between the 2 clamps that used to connect the valve to the adjacent pipes.
The only other possible use of the crossfeed duct in the air is for air starting engines. A published drill is in place to air start an engine from the adjacent engine, while keeping the crossfeed duct shut. We would be in a very complicated multiple failure situation if we had to use that pipe to start an engine from the other side, through the crossfeed duct. Nimrod peformance tables indicate that the 3 engine (climb) ceiling is above our normal cruise altitude. The aircraft is grossly overpowered and, therefore, with 3 engines running there is never any need to air start the single failed engine. Even a double engine failure just after take off at max weight in temperate climates is survivable if the drag is minimized. I doubt that most modern airliners can match that degree of performance. There is more to this aircraft, in safety aspects, that most people outside of Maritime, don't know about. sadly, the crossfeed pipe is the fabled Achilles Heel in all aspects.
Regards
Ed Sett