I heard it was Gemini, and they were doing it on a sub-charter on ACE's behalf until they were up and running with the '10's. Crews are training and there is already one on the OC.
I beleive there may be a regulation in Canada that will only allow a foreign carrier to be contracted for such work as long as there is no acceptable domestic operation that may provide the service. Just something I read in another discussion, but it may be true.