Against my better judgement, I will post the answer. Profiler isn't anymore. Everyone can direct questions to canuck_in_uk -- this seems to be his forum...
@Hkdominante: If the permit is in the CIC's mail room the day before your current permit expires, you have implied status -- means you can legally remain in Canada until they decide.
However, from: http://www.cic.gc.ca/english/resources/tools/temp/visa/validity/implied.asp
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A temporary resident must apply to extend their period of authorized stay before it ends. If they have done so, their period of authorized stay as a temporary resident is extended by law until a decision is made [R183(5)]. Such a person is considered to have implied status as a temporary resident during that period.
If a temporary resident applies for renewal of their work or study permit and their permit expires before a decision is made, paragraph 186(u) and section 189 of the Immigration and Refugee Protection Regulations (IRPR) (the right to continue working or studying under the same conditions pending a determination of their application for renewal) apply only as long as the person remains in Canada.
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Meaning you can keep working, as long as you remain in Canada (in most circumstances).