Unfortunately Acrobat has decided it won't let me open my older files on the SOR and CONOPS so you will have to take my word for this
My sense of the original government plan was that they wanted a vessel that could operate from the Grand Banks of Newfoundland all the way north to Tuktoyaktuk. Given that ice starts off of St John's, where the Titanic sank, an ice-capable hull seems to be a reasonable requirement to me.
The other sense I had was that the fleet would be a Halifax based fleet capable of transiting the Arctic Archipelago when conditions permitted and over-wintering in Victoria prior to returning North and Halifax. The fleet would have the Nanisivik harbour as a refueling depot to extend its range. The primary function, in my opinion, was to maintain a constabulary watch over the navigable waters of the North and maintain Peace, Order and Good Governance with the ability to keep foreign fishers, shrimpers and bear hunters under control and be able to operate more aggressively, in the sense of being able to penetrate the ice farther, sooner and faster, than commercial interests likely to operate in the area.
They were also to be able to call on the resources of the CAF, at priority call, in the event of military/para-military incursions: the advantage of having an RCN vessel in the area rather than a CCG vessel which would have to go to its masters to launch an Aid to the Civil Power request and then not have the skills to direct military forces to the area of interest.
As Underway and D&B both point out - these ships are not about breaking ice. They are about aggressive operations in waters contested by ice and foreign interests. And I believe that 8 was the right number and that the last two being built should be painted Grey, not Red. There is no reason why an AOPS patrol shouldn't start with being the first ship up the St Lawrence Seaway or end with being the last one out. Or being the first into, and last out of, Churchill.
The MCDVs, when they finish their time, they should be replaced by a similarly sized blue-water capable Patrol Vessel for Southern operations - but that would only require 2 or three to co-operate with allies in the Caribbean.