Thank you for the question. The current security screening policy in the Government of Canada does state that deputy heads ultimately are accountable. Every government department has the authority to make security screening decisions for itself. The current policy does encourage—for the purposes of efficiency, saving time and just consistency—that government departments accept other government departments' clearing or security screening decisions where it is appropriate.
What the policy actually states is that if an employee is being transferred, the receiving department receives the security screening file and reviews the file. If for any reason they might feel there's a reason to revisit some or all of the work that was done, they absolutely have the discretion to do so. Ultimately, the receiving department who grants the clearance to the incoming individual is responsible for that decision. There's a lot of emphasis on transferability, but the authority rests with the receiving department.