Given AF experience, it is not likely that AF "forecast" that BEST will fly one specific day a week to YVR would be honored. It could be, that I would not count on it with certainty. There will still be few retrofitted frames available and with AF policy to sprinkle them to a very large number of destinations, nothing is assured. A simple delay in delivery of one plane, some maintenance/tech problem on a couple of planes could fully disturb the schedule of that plane. And that is assuming that AF does not chnage its mind on where to send those BEST planes.
I would suggest that you set your expectations on getting an "old" plane and be happily surprised if a BEST plane shows up.