yes, I have Canadian friends went back (he has HK ID with him) to HK and got Govt jobs there...that was 10 yrs ago.
As for local civil servant jobs: it's more to do with whether you have the qualifications to meet their requirements than whether you are local or foreigner (exchange students, etc.).
I have some colleagues who came here from other English-speaking countries and landed jobs working as civil servants also...and in the process of applying for PR.
