"We need to figure out the best global structure and then determine who's best in the boxes," he told ENR. "It's premature to talk about roles."

In a note to employees, Pierson noted the importance of a buyer "that financially valued PB appropriately, but more importantly one that shared the less tangible ethic of what is important to us."

But It is not clear if changes are planned in how and where the PB name is used.

While PB “looked very hard” at private-equity ownership, “the market access with WSP outweighed the [private-equity] independence,” Pierson says. The firms are teamed in one of three consortia selected in July to bid for the $5-billion public-private partnership contract to design, build and operate a new crossing of the St. Lawrence River, in Quebec.

Shoiry sees a boost in WSP's U.S. presence to 6,200 employees with the PB deal, and added capability in Australia and the UK, where hard-hit markets are showing some positive signs.

"In the UK, there's room for some upside," he told analysts. "The private sector side is moving. We believe public sector spending will follow."

Shoiry also noted "some modest recovery in the past 3 months in Australia. It's encouraging but we still need consistency." Among other things, the country is set to sign a deal shortly to ship mined uranium to India.

Proceeds to PB's owner, London-based contractor Balfour Beatty, which acquired the New York City-based firm in 2009 for about $626 million, will aid the UK firm's bottom line after several recent profit warnings issued within the past year.

UK rival Carillion tried unsuccessfuly to acquire Balfour Beatty but negotiations ended in August over a demand to keep the professional services unit in place.

"The sale of Parsons Brinckerhoff follows the recent revaluation of our investments portfolio, which underlines the potential of this division to create value internally and across the group," said Balfour Beatty Executive Chairman Steve Marshall. "In the US, our core construction business is well positioned in a recovering market.  In the UK we see the potential for margins to progressively recover to peer group levels."

Pierson says, however, that sale discussions began “months before the profit warnings” as the firms realized they could not gain enough global benefit from their linkage. One source with knowledge of the firms says the U.K. parent “did not invest in growing PB.”

Shoiry told analysts that WSP will likely look at other smaller acquisitions in selected countries, such as Canada and the Nordic countries.

"We will come out of this deal with a balance sheet that has some room," he said.