Who is the Employer of Temp Workers?

I was on a panel last week at Lancaster House’s Labour Board Law conference in Toronto that considered important labour board decisions over the past year.  One line of cases considered the question of who is the employer of temp workers placed at a company.  The temp agency retains workers and then assigns them to a ‘client’.  The workers then report to the client and work there for short or longer periods of time.  So is the employer the temp/placement agency or the client?
The issue usually comes up in labour board hearings when the workers try to unionize and the question becomes who is the employer for the purposes of the union’s attempt to organize the workers.  In other words, who will the union be bargaining with if it obtains enough support to be certified?
We looked at two recent decisions of the OLRB:  UFCW and PPG Canada (and Liberty Staffing and Staffing Edge Inc.) and CAW and National Waste Services.  In both cases, the placement agency is found to be the employer.  In the PPG case, both the placement agency and the client (PPG) are ruled to be employers (they are common employers within the meaning of section 1(4) of the Labour Relations Act).  The decisions aren’t surprising to labour lawyers, because the Board applied the same tests its been applying for years.  
It asks who exercises fundamental control over the workers at the workplace?  The leading cases that discuss the test is (still) York Condominium Corporation, [1977] OLRB Rep. Oct. 645 and the Supreme Court’s decision and comments in Pointe-Claire (City) v. Quebec (Labour Court) 
What’s interesting in these cases is that almost invariably the placement agency and the client attempt to define the workers as employees of the placement agency, but those attempts are mostly ignored by the Board.  The contract between PPG and Liberty (the placement company) said clearly that PPG is not the employer of the workers, and a separate contract between PPG and a payroll service company (Staffing Edge) said that Staffing Edge was the employer.  The Board discounted all of that drafting as self-serving–what matters is who actually controls the workers’ day to day activities.   So, HR managers, don’t assume that temp workers are not your employees just because you don’t intend them to be, or  a contract says so.
In National Waste, the Board noted that Bill 139, which amends the ESA to make temporary placement agencies the employer for certain ESA purposes, does not effect the issue of who is the employer for the purposes of the Labour Relations Act (see para. 86-88).  [See Michael Fitzgibbon’s comments on Bill 139 here]  That mean a temp agency may be considered the employer under the ESA, while the client is the employer under the LRA.  Might seem confusing, but in fact it has always been the case that the identity of employers can change depending upon which statute is being applied.