The show was NOT canceled for lack of ticket sales, certainly not officially anyway. The official reason given was that the tour schedule had been reviewed and YES were slated to tour South America instead. All I know about it is that I read that the Edmonton visit was canceled for this reason. There was an announcement in the local paper about their impending visit (and I recall it being for January 8 and not 9th)....soon after canceled for re-scheduling reasons.
All I know is that YES haven't been to Edmonton for an extremely long time......after all, it was the FIRST North American city that the band had come to during the 1971 Tour.