US fire code laws require release of mag-locks upon loss of power, upon pushing a "PRESS TO OPEN" button, upon fire alarm, and upon motion sensor seeing someone approach the door. Quite elaborate, really, but necessary to prevent people from being trapped in burning buildings. All the interlocks do the same thing, though- break power to the mag lock. I'm not familiar with Canadian law, but I can't imagine it being more stringent than this. Breaking a common circuit path sounds like an acceptable way to do it- it would open both doors simultanously in an emergency, but allow independant operation of the other sensors.
