I'm also in BC and, NO the police cannot just walk into your property and start searching unless they can A. See the plants from outside your property; B. Can see signs indicative of a grow op from outside the property; C. have a warrant.
Probable cause in a court of law gets officers into more trouble than it does help them. You may still get in some trouble if you get caught with large amounts in BC but they can't say they smelled it from outside your property because there's no way for them to legally prove without a warrant that it was actually coming from your residence. Probable cause would be more along the lines of seeing condensation and reflective material on a window, that sort of thing.
another thing about BC. If you're not growing a substantial amount, the police don't care. I've had my house broken into and when the police showed up some of my equipment was laying in my house and they just chuckled and said "you must grow some nice tomatoes". I honestly believe they'd rather people do it themselves than buy it from drug dealers. At least when you're growing your own you're paying for power/water which gets taxed so the govt gets something from homegrows regardless.
It may be a myth or urban legend, but i've read several articles stating that in British Columbia, for personal use there are no penalties aside from a minor possession charge for up to and including 6 female plants without a license. With the license, the number you're allowed dependant on how many patients you're supplying, or how much you use personally.
If it's obvious that you're doing it for yourself, and not attempting to make phat stacks of cash the most they will do is fine you, charge you with possession(not with intent to sell) or take your plants away since the equipment itself isn't illegal and you're not growing a field of green.
I half agree with dman, If you're already growing inside you for SURE don't need the extra attention outside, but if you can set it up so they're not visible without actually being inside the greenhouse it's a good project for some extra knowledge.
if I was you I would give it a shot with a couple or four plants.... cops can`t go anywhere these days without the "right paperwork" ... 
