Hey guys, correct me if I am wrong, please.
But, whom applied to PGWP and after that your study permit expires, or even it expired before you applied, but inside the 90 days after that, you are going to have the implied status and it means (from CIC website):
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, R186(u) and R189 (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.
Source: http://www.cic.gc.ca/english/resources/tools/temp/visa/validity/implied.asp
So, all of you that was working before your application to PGWP you can still work with no problem, even if you SIN number expires you can continue to work.
Why that?
Because your status when you applied for PGWP is going to remain the same until the decision of your application.
For example (fictional dates):
Study Permit expires: 30/12/2015
Permission to Work OFF Campus expires: 30/12/2015
SIN Number expires: 30/12/2015
Last day of Classes from Post-Secondary Institution in a 2 year program: 13/12/2015
Unofficial Transcripts available: 20/12/2015
PGWP Application: 28/12/2015
PGWP Received: 15/06/2016
Between 30/12/2015 and 15/06/2016 the person who applied to PGWP is going to hold an Implied Status and keeping his or her status that he or she hold when applied to PGWP.
The user that lost a job offer because it was taking so long to process the PGWP, lost it, probably, the company that was hiring him didn't know about the implied status or the user didn't know this and didn't explain it.
If I am completely wrong, please correct me.