I'm not sure if this is relevant information, but I came across something rather interesting..
I found this CIC manual: http://www.cic.gc.ca/english/resources/manuals/op/op07b-eng.pdf
In section 7.3. it says: "When an individual is nominated by a province for selection in the provincial nominee class, the province sends the certificate of nomination directly to the visa office."
In section 7.6. it says: "When a visa office receives a certificate of nomination under the provincial nominee class, the officer should proceed to issue medical instructions and and carry out normal security screening procedures as soon as possible, provided complete application has been received."
So a visa office will not do anything to an incoming PR application, until it has received the certificate from the nominating province.
This leads me to think that OPNP hasn't been sending the certificates to Sydney/Ottawa, because the QA procedure that was carried out last year showed that there were lots of issues with people who had gained PR through OPNP in the past (mainly misrepresentation, incompetent OPNP staff, downright corruption; audit final report here: http://www.auditor.on.ca/en/reports_en/en14/309en14.pdf).
The audit was carried out between February and August 2014 (which would fit with the timeline of applicants whose files are not moving, namely May-September, since Feb-Mar-Apr applicant would've already gotten their AORs and MERs by the time initial information from the QA started trickling in) and the final report was released in December.
So CIC won't start acknowledging and processing PR files from last year until the OPNP office has quadruple-checked all the provincial nominees and become truly satisfied that the certificates upon which the files are based were rightly issued. They've probably been examining the credentials and employers etc of the applicants a lot more rigorously, hence all the QA calls and additional document requests that were put out throughout last year.
I don't have an official confirmation or source for these thoughts, but it seems fairly clear to me that the delay is at the OPNP end of the line, and not CIC. Hence CIC would not be able to give any solid answers to email/phone queries.