My understanding is that 7 sets of A stock remain but are not assigned duties so they could appear anywhere they will finally disappear after the Olympics. As it stands 54 S stock have been delivered which means there are now more trains than that needed for peak (50 trains PM peak) A stock will only be used where there is a train shortage.
On a slightly related note (in that it concerns trains to be scrapped), there is a group of people who have been actively working towards the day when the HSTs are finally replaced. They intend to buy a complete set and use it for heritage purposes.
There should be a similar group for tube trains, although as the A-Stock can only run on the LU network under its own power, it would probably be LU themselves who would deal with this. My guess is they're not too bothered about preserving one.
One thing only do I know, and that is that I know nothing - Socrates.
Champion of bugger all, 2004 to 2026
Member of sweet FA
That is correct - they are aiming to get it certified for mainline use.
Having said that, when they "electrify" the Western region, it won't all be electrified. Most of the south west will require diesel trains, so the HSTs will still be going for a while yet, subject to a major overhaul of internal parts to make them last a bit longer.
If the preservation group obtain an HST before they are entirely withdrawn, then they will be able to run it on the main line, so long as they maintain it to the standard required.
One thing only do I know, and that is that I know nothing - Socrates.
Champion of bugger all, 2004 to 2026
Member of sweet FA