Not sure where the idea comes from that IEC WP cannot get implied status... There are absolutely no restrictions on this in the immigration act !
Those are open work permits, with a specific LMIA-exempt code, under the Mobility program. They are delivered for a specific period, and obey specific requirements of eligibility. Other than that, it follow the same rules as any WP.
So yes, it cannot be extended, that's part of the eligibility criteria. But you can change the conditions of your stay and ask for another work permit, or a study permit, or a visitor visa...
Therefore, if you do so before your WP expire, implied status is applicable, like it would for any WP.
If you should know, I have had implied status for almost 2 months after my so called working holiday visa. My WP application got denied because of LMIA, and I received a letter from CIC stating I only had a valid status until the date of the letter (so not the date of the IEC WP). That letter confirms the implied status.
Though, if you ask for new WP and cross the border, you completely loose the implied status. Meaning if you have worked during the implied status, you have just made yourself an illegal immigrant during that time ! That's probably why some people had issues.
You have to make your application online and remain in Canada until a decision is made.