The most common scenario—you have to put your mind back to the pandemic period—would have been employees who were laid off before the wage subsidy program was announced. Then, when the wage subsidy program was announced, they were brought back retroactively. That was a deliberate design feature of the wage subsidy program to kind of maintain employment.
A very early example of how you could be—legitimately, through no fault of your own—in double receipt would have been if, when you were laid off; you claimed CERB, and then your employer subsequently claimed the wage subsidy and brought you back onto strength retroactively and gave you your normal paycheque. That would be an example.
We're still working through how many of the various scenarios have manifested themselves, so I think it's too early to comment on how many different scenarios there are and what the total dollar value is of the double claims. It's not possible to tell, without a detailed examination of somebody's T4 history, which sources of income came from which employer. Time will tell.