Gas Range 20 amp Circuit Breaker

Steven - I am also in Vancouver, and just installed a new kitchen with permits and inspections. Yes, the gas range and hood can be on the same 15A circuit, as mine are. Just be sure that the oven is also gas, and does not have any electric broiler or electric self-clean. If the rating is under 12A you are fine. If you are splicing into an existing 15A circuit, you can install as many junction boxes as you need, so long as they are accessible by pulling out the range, or by removing the range hood's fake pipe, or by opening the door of a cabinet above the range hood. My splice is in the receptacle box that the Ikea hood fan plugs into.

I have always had gas ranges, built-in ovens and cooktops, and have never heard of CO being a problem. It should only be a problem if the flame isn't getting enough oxygen.

In the basement, you probably have a gas furnace, gas HWT and gas dryer. They all suck air. If you add a range hood and a bathroom fan, you could be seriously short of makeup air. I was required to add a 4" fresh air vent in the new basement suite. I put it behind the fridge, so that the cold incoming air would mix with the heat from the back of the fridge, avoiding cold drafts.

UPDATE: @doozit commented below that this document was just a proposal, which wasn't accepted. (It isn't described as such on the ESA webpage)

A quick google search found what looks like the answer in the Ontario amendments to the Canadian electrical code on the Electrical Safety Authority's page

This reference might be enough for you and your electricians to break the tie:

31.Delete CE Code Rule 26-744(4) and replace with the following:

(4) A receptacle of CSA Configuration 14-50R, as shown in Diagram 1, shall be installed at a suitable location in every single dwelling and in every dwelling unit of an apartment or similar multi-dwelling building for supplying electric energy to an electric range.

32.Add Rules 26-744(10), (11), (12) and (13) as follows:

...

(13) Notwithstanding Subrule (4), the range receptacle need not be installed in

(a) dwelling units where a built-in gas-fired or electric cook top or a built-in gas-fired or electric oven is installed;

(b) other than single dwellings where provision has been made for a gas range; or

(c) dwelling units where power from a supply authority is not available and the capacity of local generation is less than 6 kW.

So it looks like you don't need the receptacle as long as a cooktop or oven is installed.