No, it's not a lottery system, in fact they have a clear system and that is if your NOC is interesting/needed/underrepresented you will receive the certificate, even though you're already in your final stages of PR application (see previous post). I also doubt that AINP is giving certificates for expired work permits. That was maybe possible before, lets say a year and a half ago but defs not now. In fact, for the first six months of this year AINP was giving out nominations based on wp expiry. Short and brutal conclusion: if they want you, they'll give you a certificate, otherwise they'll allow for your wp to expire and for you to try to extend your stay as much as possible, pay taxes, contribute toba canadian company, and all that based on false hope and wrong opinions like getting a certificate is like winning a lottery, so far from reality.
