Al Qaeda "sleeper cells" in Canada and the United States have communicated with each other as recently as this month, probably to plan terrorist attacks in the United States, Canadian intelligence experts said yesterday. The disclosure came in the wake of the arrest last week of a pizza delivery man in Ottawa who is suspected of being associated with the terrorist network of Osama bin Laden. Canadian authorities decided to arrest Mohamed Harkat, 34, shortly after he made calls to suspected al Qaeda members in the United States, said Reid Morden, former director of the Canadian Security Intelligence Service, who...