I'm a licensed pilot (not flying for the airline though). The interference between mobile phone and onboard nav/comm system is almost entirely theoretical. In practice is really an non-issue, unless during an instrument approach under very poor visibility when you want to eliminate even a miniscule chance of interference (such as landing in visibility less than 1/4 mile on surface - category II or III ILS approaches).

As to the passenger - he/she can get fined by the FAA or Canadian aviation authority. As long as such rule exists the passengers must abide by the regulation.