ITA is not the final decision to extent work permit, while someone get ITA they can't extent work permit with ITA, after received ITA they have to apply for Fedaral immigration, hence the person receive file number then they will be able to apply for open work permit, meanwhile PGWP or any other WP has to be valid, if WP not valid, applicant has to leave Canada.Which means 3 months before expired WP, should prepair to extent it. Not like someone has 2 weeks , says after 2 weeks my WP experiang I didnt get ITA.