The delay follows an announcement in January that BT is to sell its property division.
The Carillion-led consortium, which includes Balfour Beatty subsidiary Haden Building Management and Reliance Integrated Services, was named preferred bidder in May last year, and the contract to manage and maintain 8500 of BT's properties was due to be signed last October.
A source close to BT said one reason for the delays was the decision to sell the property arm.
He said talks on the five-year contract centred on how to transfer it to the whoever bought BT's property division. This could involve changes to the contract.
Trillium and Mapeley are bidding to take over the property arm of BT.
The source said: "Jaguar has not been signed – the game is open, most probably because of the Trillium/Mapeley bid for BT property. I would have thought that the firm that takes over the property arm would want to vary the terms of the contract. I think it will take them on as part of its supply chain." A spokesperson for BT confirmed that the contract had not been signed but played down the impact of the sale of the property arm.
The firm that takes over the property arm would want to vary the contract
However, he admitted that there could be changes to the detail of the contract because of the sale.
He said: "The fine detail is being sorted out and it is on track to be signed." A spokesperson for Carillion said the consortium was carrying out the work under an interim contract. He added that the full contract was on course to be signed.
The spokesperson said: "BT has assured us our role is unaffected by the property sale. It is very complicated and it has taken a lot longer to close than anyone anticipated." The Carillion team will split the contract into eight regional centres.
The regions will be split between Haden, Reliance, Carillion, Mitie and Rentokil Initial.
Each regional provider will have to deliver year-on-year savings, meet key performance indicators and work to a guaranteed maximum price.
Carillion saw off competition from Amec, Bovis Lend Lease and Mace/Citex for the deal.