Hi Guys,
We had this discussion 1 year ago and many conflicting suggestions as well, see link: (http://www.canadavisa.com/canada-immigration-discussion-board/-t92945.0.html).
To answer the question simply - YES, a postdoc is qualified to apply under CEC with T4As. I did receive T4As and have successfully become a PR.
Regarding NOC, CIC suggests that postdocs chose an NOC representative of their educational qualification (of course that works if your research is in sync with your degrees). You can of course use any NOC that best describes the work experience you are claiming.
I hope this puts daylight to the questions and confusing comments regarding postdocs and T4As. Universities define their use of T4 or T4A for postdocs, depending on the source of funding and as most postdocs have already noted, you also pay the full tax regardless of T4 or T4As.
This must not be confused with self-employment T4A