Does anyone know what the city of Ottawa, Ontario, Canada will accept as the minimum frost protection depth for the bottom of footings on new construction?

Why don't you ask the city of Ottawa?

That was my plan, but of course they are not answering calls on the weekend so I thought I'd get an advance answer from someone who may know.

about 48" I think

48" should be sufficient. Alberta building Code calls for 48" and the climate is very similar. The only place I know in Canada with less than 48" is parts of BC (36"). Your best bet would be to contact any certified builder in the area, but I am sure that if you plan for 48" you will be fine.

I live just south of Edmonton and it is 48 inches here.

The City of Ottawa bldg dept. indicated that the frost depth is set at 5ft minimum for heated structures and 6ft for unheated construction.
cheers!

Who cares - use a frost protected shallow foundation. Of course then you have an insulation thickness and distance out you have to ask about.

You'd have to get this spec'd by an engineer. I'm pretty sure it isn't defined in the current codes as a simple solution. Can't fathom why anyone wouldn't build this way these days though. Why people continually build clay swimming pools and call them basements baffles me.