The Foreign Worker Manual provides the following information about extensions under the permits issued for IEC programs:
Conditions of work permit: participants under the working holiday category may receive an open work permit with a validity period of 12 months (See Appendix E for details); participants under the one of the other two categories may receive employer-specific work permits with a suggested validity period that reflects the length of their contract of employment. Participants holding an employer-specific work permit must submit an application either online or by mail to CPC-Vegreville if they wish to change the conditions imposed on their work permit (e.g., change in employer).
(Use the following link for instructions on how to do this:
http://www.cic.gc.ca/english/information/applications/extend-worker.asp). The validity period of a C21 work permit may not exceed the validity period of a participant‘s passport. IEC participants may not request to extend their stay under IEC unless the extension is within the original authorized period of stay as per their LOI.
So being able to extend the terms and conditions is based upon the original LOI - letter of introduction. If you meet the criteria for the LOI then implied status exists if the application was submitted prior to expiration, however, if criteria is not met then there is no implied status.