Commercially the deal makes sense and the merged operation may be able to save up to £3.5m a year by cutting out any duplication.
Since then, the companies have been trying to forge a deal that would give each 50 percent control over the merged operations.
CanWest estimated that the combined strengths of the merged operations could save the company up to $100 million a year.
As is occurring at other offices, executives from Lowe units will dominate the merged operations.
"We think there is an opportunity to take significant cost out of the merged operations," Mr. Leatherdale said.
The merged operation in Canada will be a division of BPA, under its current name.
Current IESI shareholders will ultimately own 39 percent of the merged operation.
Following the purchase, the merged operations will have annual sales of more than $800 million.
The merged operation, not yet named, will be 65 percent owned by Havas.
The merged operations employ about 40 people on Long Island, about half of the pre-merger total.