I really can't believe what i'm reading here, the what if this, what if that, scenario's is totally irrelevant, you install any system installation as to the project drawings, what happens after, is not your problem or responsibility!! Your making up these scenarios to suit your argument, but frankly in the real world there is no argument to provide pointless CPC provisions where none is required or needed, ...end of!!
Fly leads are fly leads, of course they are required at accessories and fittings. Even if flexible conduits were completely plastic, what would be the trouble using the threaded earth connection of a BESA or any other box/enclosure for your CPC connection to equipment via short lengths of flexible conduit?? Been used successfully for this purpose, for connecting say motors and other required equipment for bloody years, so what's suddenly changed now then??
If sections are removed and replaced with PVC containment, then it is the responsibility of the electrician making those changes, to provide CPC provision. Same goes for any other alteration to an existing metal containment system. None warrant running in separate CPC's to the system in the first instance...
Were running in miles of metal containment systems, and when i say miles i mean miles!! Do you really think it makes any economic sense to run separate CPC's?? Bloody hell, the size of the conduits would need upgrading to the next size in most cases, just to keep within the fill restrictions. Needless to say, there will be no separate CPC's in our metal containment systems (trunking and conduits). You and others, that are foolish enough to do so, can get on and do whatever you like, ...all i can say, something has gone very wrong somewhere along the line on metal containment systems in the UK!! You've all gone stark raving Mad!! lol!!