Rail union RMT has threatened industrial action if jobs are cut following the failure of the botched public-private partnership (PPP) on London Underground.
All Tube maintenance and upgrade work will be brought back in-house after the controversial PPP on LU ground to a halt.
Transport for London (TfL) announced late on Friday that it would pay £310 million to the firm's owners, US firm Bechtel and Spanish-owned Amey (Ferrovial), in return for their shares.
The deal brings to an end the £30 billion PPP under which large sections of Tube engineering work were sold off to privateers on 30-year leases.
Tube Lines was responsible for carrying out upgrades to the Jubilee, Northern and Piccadilly lines.
Its counterpart Metronet collapsed in 2007 landing taxpayers with a bill running into hundreds of millions.
However TfL claimed that Friday's agreement would not bring extra costs for the government or taxpayers, but would create massive savings otherwise wasted by the destructive PPP.
TfL pledged to take a "different approach" to the Northern Line upgrade programme in order to reduce the impact of Tube closures.
Work on the Jubilee Line to be carried out as a priority, TfL added.
RMT general secretary Bob Crow described the collapse of PPP as a sign "on a massive scale" that transport privatisation does not work.
He added that the union is set to ballot its members unless assurances are made on the jobs and conditions of the 3,000 Tube Lines employees.
Mr Crow said: "We know that Mayor of London Boris Johnson is still looking at multibillion-pound cuts.
"Staff should not be made to pay the price of the collapse of the disastrous PPP."
Business group London First chief executive Jo Valentine said the upgrades must now be prioritised if London is to grow.
"This acquisition represents a welcome shift from continuing public acrimony.
"It offers clarity and puts the onus squarely on Boris to deliver the better Tube which London businesses and commuters need," she added.
Mr Johnson said the arrangement "provides the greater flexibility we so desperately need to minimise disruption."
The PPP model was bitterly opposed by former mayor Ken Livingstone who advocated raising the money via bonds.
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Andrew Lansley's last transparent fig leaf has been blown away by a gust of realism from the Royal College of General Practitioners (RCGP).

