SNC-Lavalin Group Inc. has signed a deal to sell part of its stake in 407 International Inc. to the OMERS pension plan.

Under the agreement, which has certain conditions, SNC is selling a 10.01 per cent stake in the toll highway operator in a transaction worth up to $3.25 billion.

The agreement will see SNC-Lavalin retain a 6.76 per cent stake in the company, which operates a toll highway in southern Ontario.

OMERS will pay $3 billion to SNC on the closing of the deal and an additional $250 million over 10 years, conditional on certain financial targets related to the performance of the toll highway.

The OMERS agreement with SNC is subject to certain rights of 407's other shareholders, including rights-of-first refusal.

The other owners of the toll highway include a subsidiary of Ferrovial S.A., with a 43.23 per cent stake, and the Canada Pension Plan Investment Board with a 40 per cent.

SNC says part of the net proceeds from the sale will be used to repay debt.