Quebec, in particular, has shown reluctance to use the 2008 guidelines in its court hearings and family-practice mediations.
"From survey responses, spousal support cases in British Columbia and Ontario are more likely to be settled within the (guideline) ranges for both amount and duration than cases in other parts of Canada," says the internal Justice Department report.
In Quebec, on the other hand, there is "very limited use."
The study examined the impact of the federal government's spousal support advisory guidelines, an $800,000 project begun in 2001 to provide more consistency and fairness in marriage-breakdown settlements.
Unlike national guidelines for child support, which are virtually mandatory, the spousal-support version provides only advice to judges, lawyers and mediators.
The Justice Department commissioned the study from Prairie Research Associates to discover how often marriage breakup settlements now rely on the dollar ranges outlined in the July 2008 final version of the spousal-support guidelines.
Prairie Research interviewed 34 key members of legal communities across Canada, and surveyed another 461 by email.
A copy of the January 2012 report was obtained by The Canadian Press under the Access to Information Act.
The researchers found the guidelines generally working well, with British Columbia an early adopter.
The West Coast province's distinct property law has sparked a lot of spousal-support litigation, and the B.C. Court of Appeal was quick to endorse a 2005 draft version of the guidelines as a way to reduce courtroom conflicts. The B.C. legal community quickly climbed aboard.
The Ontario Court of Appeal in 2008 similarly endorsed the guidelines, prompting widespread adoption in Canada's largest province.
But the study also cites lagging use in other provinces, especially Quebec where the province's appeal court dismissed the guidelines in a landmark 2006 ruling.
Where the guidelines are in general use, they have helped to improve the consistency of awards and to reduce conflict, the study found.
"Key informants noted that the (guidelines) aid spousal support negotiations by providing an objective starting point for discussions, narrowing the range of possible outcomes, and helping to shape client expectations about amount and duration," says the 41-page internal report.
Rollie Thompson, a Dalhousie University law professor who co-wrote the guidelines under a Justice Department contract, traces the project back to a Supreme Court of Canada decision in 1999 that sowed confusion about appropriate settlements.
He also noted that an August 2011 Quebec Court of Appeal decision, not captured by the study, has since erased many of the court's previous objections to the guidelines.
"It has to some extent broken the logjam in Quebec," he said in an interview from Halifax, noting that the guidelines are gradually being adopted elsewhere as well.
The guidelines "narrow the scope of disagreement" in spousal-support cases, he said, and have helped some deserving spouses achieve modest levels of support that would have otherwise been too expensive to pursue.
"People who probably deserve spousal support are now able to get it," Thompson said. "Previously it would cost you thousands of dollars (for legal help) to get a few hundred dollars a month."
A lawyer in Toronto says the introduction of the guidelines has transformed his family practice.
"They changed our work immensely because spousal support up to that time was a bit of a guessing game," Grant Gold said in an interview.
"You had no idea what the test was. You had no idea what the amounts were going to be. ... It was a large crap shoot when you went into a trial, or even when you went into negotiations."
Gold said there was some initial reluctance in Ontario to adopt the guidelines, but attitudes have shifted dramatically.
"This has changed the whole landscape of spousal support," he said.
Thompson, who still researches the impact of the guidelines he originally developed with Carol Rogerson at the University of Toronto, says they can serve as a model for other countries.
"There's real interest in these guidelines in other areas of the world," he said.
"Canada leads by example."