The settlement, first revealed in Building last week, is part of an attempt to ensure that all sections of the line, including Westminster Station, are open for the next millennium.
However, US troubleshooter Bechtel, which stands to lose a £10m bonus if the line does not open this year, will not have to dig into its own pocket to pay the electricians.
A JLE insider said Bechtel, which is earning £13m in fees, refused to foot the bill that could amount to £500 000 and that Drake & Scull will pay it instead. The insider said: "The client will not be paying for the new deal. Drake & Scull is going to take it on the chin because it wants to deliver Westminster this side of the millennium."
Bechtel and Drake & Scull were unavailable for comment. However, the insider said that 100 electricians scheduled to be made redundant on 19 November will now stay on until 29 November to complete the delayed Westminster Station.
One electrician said: "We are earning money that is based on productivity targets agreed by Bechtel and Drake & Scull. Of course, it is extra money for us, but our bonuses will be a lot less than Bechtel's £10m."
Drake & Scull is going to take it on the chin because it wants to finish Westminster
Work at Westminster has been dogged by delays and London Underground chief executive Dennis Tunnicliffe has admitted to parliament that it may not open in time for the new year.
Last week, London Underground announced that the final phase of the line linking Green Park with Waterloo will open within the next fortnight, although it conceded that a number of stations, including Southwark, may not open until later.
The open part of the line is also experiencing problems and has broken down more than 40 times since it opened earlier in the year. The computer communication system, which collects and distributes signals and communications, crashed in tests and one insider said it was unable to cope with large amounts of information.