Electrification plans don't remove DMUs from Reading completely, because there is still the North Downs line to consider. I think 150001/2 are more likely to be transferred somewhere else (for fleet commonality at Reading) as a result of less DMUs being needed there well before wiring starts.
--- old post above --- --- new post below ---
Like for like renewals are permitted, as are short extensions. In fact new DC equipment has recently gone in , and is still going in, on various routes to strengthen power supplies to allow train lengthening projects to happen.
Although much of the SWML equipment is life expired, there is something like a 30% overlay of new equipment fitted only within the last ten years or so, and that is likely to go into the maintenance and renewals stockpile for other DC routes.
The 3rd Rail to 25KV conversion Basingstoke to Southampton will be done at some point, perhaps towards the end of CP5 but there is no dates given as yet.
This was the original announcement by the then secretary of state in 2012 for the Electric Spine:-
The Secretary of State wishes the industry to develop and deliver within CP5 the major rail electrification and capability enhancement referred to as the Electric Spine, in order to increase regional and national connectivity and support economic development by creating a high-capability 25kV electrified passenger and freight route from the South Coast via Oxford and the Midlands to South Yorkshire.
The routes to be electrified as part of the Electric Spine are:
Southampton Port Basingstoke (conversion from 750 dc);
Basingstoke Reading;
Oxford Leamington Coventry;
Coventry Nuneaton;
Oxford Bletchley Bedford (East West Rail core route);
Bedford Nottingham and Derby, and Derby Sheffield
(Midland Main Line); and Kettering Corby
The southern end of the Electric Spine entails the conversion of a section of the existing Southern third rail (750V DC) electrification system to the more modern and capable overhead (25kV AC) system to upgrade its capability. The Secretary of State also wishes the industry to develop a longer-term proposition and business case for the systematic upgrade from DC to AC of the whole Southern network, for consideration for future control periods. As part of this work the industry will wish to treat the conversion work required for Southampton to Basingstoke as a pilot scheme for such a potential modernisation programme, and review plans for renewing or upgrading the DC network to avoid the risk of nugatory expenditure.
On another issue, after years of no interest in any electrification, everybody seems to want it now and done within short timescales, Network Rail can only do so much, we have already seen some projects slip back, except a few more in the next 5 years!