The report establishing the framework for evaluation of CalgaryNEXT was authored by the Mayor's Office and approved by Council. It included recommendations to consult affected organizations. This is partially what led to the notion of looking formally at a Plan B.
http://agendaminutes.calgary.ca/sire...A&itemid=38022
The evaluation and subsequent feasibility report was done by Deputy Manager City Brad Stevens.
The conversations at early stages were almost exclusively between the Mayor/Mayor's Office and CSEC. Once it moved into the formal evaluation phase, the Deputy City Manager along with supporting work from entities like CMLC and direct input from organizations like Calgary Economic Development, U of C, and Stampede. This is where the Plan B - explicitly identifying Stampede for a standalone arena, Fieldhouse at Foothills and a renovated McMahon emerged.
http://agendaminutes.calgary.ca/sire...a&itemid=43230
Formally, Plan B was Administration derived, but I have little doubt (even though I have zero inside knowledge on this) that the Mayor has continued to remain closely involved in all discussions. So not totally cut and dried.