A list of people who are on the specified persons list is provided to the airlines. Before every flight, the airlines will reconcile the people who are on their flight against the specified persons list. If there is a possible match, they will phone the Transport Canada operations centre, which is a 24/7 operations centre, to obtain further information about whether the person who they feel is a possible match is actually a person on the list. In most cases, the time taken to resolve those questions is usually about three to five minutes, so it has never resulted in a case of delayed boarding.
On April 29th, 2010. See this statement in context.