Locked Out Sears Workers Take to You-Tube in Fight with Sears

On April 1st, Sears Canada locked out some 500 workers at its distribution centre just North of York University in Vaughn.  A lockout means that the employer is refusing the employees the right to come to work, and is not paying them.  My employment law students know that if a nonunion employer refused to allow its employees to come to work, that would be a fundamental breach of the employment contract and employees could treat that action as a

constructive  dismissal.  But the Labour Relations Act allows unionized employers to do this as part of the process of resolving bargaining disputes, provided that certain preconditions have been satisfied.
The workers are represented by the United Steelworkers, which has taken to the internet in its fight against Sears.  Check out this You-Tube video prepared by the Steelworkers in support of its members at Sears warehouse, and the many others that will appear as related videos on the You-Tube page.  There is also a “Boycott Sears” Facebook page.
There is some suggestion in the u-tube videos that Sears is busing in replacement workers to operate the business during the lockout, though I can’t confirm that.  (Does anyone know for sure?)  In Ontario, a company is free to continue to operate during a lockout by using  employees who are not lockout out, or to use “replacement workers” (often called “scabs”) who are hired to replace the locked out workers.  The Labour Relations Act says only that an employer cannot use a “professional strike breaker”, which is a business or person who main business is providing or being a replacement worker.  Other provinces, like B.C. and Quebec limit or ban the right of employers to hire replacement workers during a strike of lockout.  For example, take a look at Section 68 of the B.C. Labour Relations Code, and Section 6(3)(e), which makes it illegal to hire a replacement worker as defined in section 68.
Can you think of arguments in favour of a ban on replacement workers, and against a ban?  Which model do you think makes more sense given that the purpose of the law is to encourage quick resolution of collective bargaining disputes?