http://www.cic.gc.ca/english/resources/manuals/op/op12-eng.pdf - page 29 said:
Specific eligibility criteria
• If the program of study is two years or more, the student would be eligible for a three year work permit.
• If the program of study is less than two years but at least eight months, the student would be eligible for a work permit lasting for a period equal to the duration of their studies. The validity period of the work permit must not be longer than this period. For example, if the student graduated from an eight-month certificate program, they are only eligible for a work permit of eight months' duration.
Exception: Students holding a one-year graduate degree from a provincially accredited post-secondary educational institution in Canada (pursued full-time) after having obtained, within the prior two years, a degree or diploma from an accredited post-secondary educational/training institution will qualify for a three year work permit. This exception also applies to students who have left Canada temporarily between the graduations.
Example: A student who obtained a one-year MBA from a provincially accredited post-secondary institution in Canada after having obtained a one year university diploma, no more than two years before obtaining the MBA, would be allowed to cumulate both degrees and therefore to get a three year PGWP.