No. The BMWCC has held April events at Mosport for about 20 years now. It can be cold and wet but there is never snow or ice.
Tremblant is a little different geographically than Mosport....and freezing rain in May anyplace is a complete fluke. One incident does not equal a trend.
Anybody who hasn't signed up by now will not be attending anyway, unless they get in at the last minute off the waiting list.
SIFO (slow in fast out)