Paul has put it better and beat me to teh post but here goes on my take.
Railcornwall is right Netwrokrail is responsible for the power supply, trrack and signalling (new Waterloo) betweem East Putney and Wimbledon. If I remember correctly from my days in Waterloo there are special isolating sections between East Putney and Putney Bridge to isolate the power supplies.
As well as
ECS▸ the following
SWT▸ passenger trains use the line.
Point Pleasant Junction - East Putney (152,155,158) WH
0454 SuX Basingstoke - Waterloo
0105 SX Waterloo - Southampton Central
0042 SX Waterloo - Strawberry Hill
Courtesy of PSUL website
http://www.avoe05.dsl.pipex.com/2010.htmWell worth a look.