The acquisition is SNC-Lavalin's biggest so far.

The Montreal-based company, which had until May 1 to finalize its offer made on April 3, would benefit from Atkins’ broader exposure to U.S. and U.K. infrastructure markets and being able to move away from oil-and-gas work, while the British firm would gain size to bid larger projects.

SNC-Lavalin says the acquisition will create a $9-billion professional services and project management giant with 53,000 employees that will "significantly improve" its margins and "further balance its business portfolio" in infrastructure, rail and nuclear sectors. The combined entity would remain based in Montreal.

Montreal pension fund manager Caisse de dépôt et placement du Québec is offering $1.1 billion to fund the deal, backed by SNC-Lavalin's cash flows from its 16.7% interest in the Toronto toll road Highway 407 concession, according to Canada newspaper The Globe and Mail, which adds that the fund also is investing nearly $300 million in equity.

Atkins ranks at No. 11 on ENR’s latest list of the Top 150 Global Design Firms, with $2.7 billion in 2015 design revenue, 40% in transportation and 24% in power. SNC-Lavalin ranks at No. 12 on that list, reporting $2.69 billion in global revenue, mostly outside Canada, with significant construction revenue not included in that total. Atkins, which was in merger talks earlier this year with U.S.-based CH2M, faced turnover in its North America leadership. SNC-Lavalin is pushing past its five-year ethics scandal.

Atkins CEO to Step Down

When the deal is completed, Uwe Krueger will step down as Atkins CEO and director, although he and SNC-Lavalin are set to "discuss putting in place a transitional services agreement," says the intended new parent. Krueger, a physicist, has served in the role since 2011. Current Atkins Chief Financial Officer Heath Drewett is set to lead the firm within the combined entity and join the SNC-Lavalin executive committee.

"By combining two highly complementary businesses, we will increase our depth and breadth of services to position us as a premier partner to public and private sector clients," says SNC-Lavalin President and CEO Neil Bruce. "It also creates new revenue growth opportunities in key geographies by positioning us to capitalize on increased cross-selling and the opportunity to win and deliver major projects in new regions."

Atkins Chairman Allan Cook says the combination "wil provide clear benefits to our shareholders and enhanced opportunities for our employees as part of a larger group and a broader service offering for our customers."

In its announcement, SNC-Lavalin does not expressly note layoffs, saying that Atkins’ employees "will be a key factor in maximizing the opportunities that the acquisition will present," adding that the combined firms' executives "will also aim to retain the best talent across Atkins and SNC-Lavalin." The new combined firm also says it agrees "that for at least two full financial years" after the deal's effective date, not to "reduce any terms relating to notice periods or pension accrual or contributions."

But U.K. media speculated that the April 24 disclosure of a 6.8% stake in Atkins held by Elliott Advisors, the British arm of U.S. activist investor hedge fund Elliott Partners, could spur a counter offer.

Atkins’ per-share price rose 1.6% over the SNC-Lavalin offer at trading close on April 24. Elliott declined comment