Basingstoke to Southampton is not fully cleared for OHLE. I had that info from one of the guys working on the new road bridge at the London end of Winchester. Each individual bridge or tunnel was treated on its own merits, and some will need re-visiting for wiring.
In broad terms anything that was fully rebuilt is clear for wires, but if track lowering was able to provide W10 clearance that was all that was done. I'm not convinced Southampton tunnel is wirable - although it may be that its OK for bar conductor.
I was off slightly when I stated that all the works had been done, however the fact that a number of bridges have already been rebuilt for OHLE and there is now at least the possibility of bar conductors in the tunnels (failing that it is at least known how "easy" it is to lower track in tunnels with the currrent equipment). All of which adds up to lower electrification costs and the potential of "easy wins" for routes which are cleared for larger freight loads, making such routes a little more likely to be electrified sooner rather than other routes which may still have a lot of bridge works to undertake.
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Had a quick look on google to find a list of classes that use Waterloo, couldn't find any list...
All EMU classes listed on the SWT's Wiki page, other than the ex London Underground stock which is solely used on the island line, would all enter Waterloo. To miss quote:
"all tracks lead to Waterloo" (well at least for every class of train which SWT's uses on the mainland)
http://en.wikipedia.org/wiki/South_West_Trains#Rolling_stock_details
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Even if the South Western side of Clapham Junction is converted to AC, there might still be signalling interference issues with the Brighton side.
Given Crossrail 2 will be within tunnels by Clapham Junction there isn't even the need to wire that far up in SWT's land to allow all of Crossrail's routes to be run by OHLE.
Also it doesn't seam to be much of a problem for Reading which has 3rd rail trains and is due for OHLE to happen soon.
Looking at Crossrail 2 maps it would appear that it would be AC conversion for:
- Woking to Wimbledon (which probably means Basingstoke to Woking to remove the need to swtch from AC to DC more than twice)
- Twickenham to New Malden (which may include from Shepperton to remove the need to switch from AC to DC and is fairly self contained)
- Epsom to Raynes Park
- Cheesington to Motspur Park
Which is quite a significant serction of SWT's network, but it has to be remembered the Crossrail 2 is likely to be late 2020's (i.e. towards the end of CP7) before testting starts.
Even then all of the services from the line to Reading and its branches would still remain as 3rd rail, so there is plenty of space for trains which still had life in them but were unable to be converted for OHLE running (455's would be about 45 years old*, 456's would be about 35** and the 458's would be about 30 years old***)
* given their age it could be that the 455's are replaced with new dual voltage trains with the same trains (not dual voltage) being delivered for use by Crossrail 2 (at least 364 coaches would be required just for the replacement of the SWT's stock before the added requirements of Crossrail 2 are taken on board it is likely to be quite a significant train order), it may mean that delivey of the trains are over (say) two years.
** give that there are only 24 sets it wouldn't be a total disaster if they were retired a few years early, although chances are they could be moved elsewhere in 3rd rail land as they are one of the few 2 coach sets of EMU's, however there could still be use for a number of them on routes likes like those between Guildford and Ascot.
*** as Reading to Waterloo will be able to be retained as third rail for some time after 2030 if need be (i.e. conversion to AC for routes to Guildford, Alton and south coast routes can all be undertaken within the SWT's network before even thinking about other TOC's networks), so they could live out their lives within the SWT's network.