I imagine the 789s will run out of YVR, YYC and YYZ with some "trans-continental" service the way AC does and WS does now with their 767s between YYZ and YYC in winter. I expect you will see a lot of them going to Europe in summer out of YYZ and I expect at least one Asian route out of YYC because YVR is pretty saturated (and Saretsky hinted at this already). Winter I'd expect high traffic sun routes (expanded service to HNL or OGG and Carribean in east).