I've never heard of a non-winter driven Ontario car having rust problems. I'm familiar with a 2000 F-150 that hasn't been winter driven and never undercoated, and it looks as good as you can expect an 18 year old truck to look underneath. I don't think if it had been rust coated if would make any difference at all, other than making a mess of the garage floor, and getting filthy when working on it. The one benefit I can see is the lubrication of fasteners. I know lots of people that don't winter drive their vehicles, and none undercoat them.
If rust is your concern above all else, then I suppose it may be worth it, but for me, definitely not.