After hiring an alleged ISIS recruiter, Ontario's largest electricity provider tried to bring in a much more intensive security screening process to protect its grid — but a labour arbitrator has found Hydro One's national security background checks were "intrusive" and "unreasonable."   The decision comes as Canada's intelligence agencies have increasingly warned that critical infrastructure in Canada is vulnerable to attack from foreign states, and that private companies need to take national security and insider threats seriously.   But as the decision — issued in late January and made public only recently — shows, there's still a gulf when it comes to balancing those concerns with labour and privacy rights.  "There can be no doubt that Hydro One’s business is highly safety sensitive and is part of Canada’s critical infrastructure," wrote arbitrator John Stout in his decision.…