gunnut,
remember, there is actually very little ozone. IIRC from my science days there are only 3 ozone molecules / 10,000,000 O2 molecules up in the ozone layer.
and also, remember that ozone up there is constantly forming and getting destroyed. it's in a dynamic equilibrium. sometimes O2 will be hit by light and break down into individual oxygen molecules (O). however, O by itself is quite reactive, and can react with other O2 molecules to form O3, or ozone.
that's how the dynamic equilibrium is formed. the introduction of chlorines into the atmosphere upset this equilibrium, simply because there isn't that much ozone to begin with.
as for smog, it doesn't just consist of ozone molecules but other molecules such as nitrates and aldehydes, especially nitrogen oxides...so i don't think fighting smog with CFCs is a great idea
