Speaking with one of our agents yesterday, he mentioned that ANA and JAL each had a 747 in YYC due to some Conference being held in town there.
Not sure if these are the charters you are inquiring about, but true enough it was there...
"Irregardless, it's a Cat III airplane, we don't need an alternate!"
Probably some during the high summer season and once again when the leaves starting changing color. NH has capacity to spare these days. They have at least one 744 and two 772ERs operating domestic route inbetween int'l charters and covering for domestic aircraft undergoing maintenance.