Here's a comparison in flight time between WJ and AC for the redeye YVR-YYZ flight over the past few days.
06-Dec-2008 AC3:50 WJ3:53 AC-3
05-Dec-2008 AC4:08 WJ3:59 AC+9
04-Dec-2008 AC4:12 WJ4:11 AC+1
03-Dec-2008 AC4:14 WJ4:10 AC+4
02-Dec-2008 AC3:54 WJ4:07 AC-13*
01-Dec-2008 AC4:07 WJ4:00 AC+7
30-Nov-2008 AC4:06 WJ4:10 AC-4
29-Nov-2008 AC4:10 WJ4:02 AC+8
28-Nov-2008 AC4:08 WJ4:04 AC+4
*On 2 December, AC operated a 77W which could explain the difference.
It does appear that AC is taking a few minutes longer. AC generally operates a 763 on this flight (normal cruising speed Mach 0.8) whereas WJ uses a 737-700 with a lower normal cruising speed (Mach 0.785).