It doesn't make sense for UA to fly into YWG when AC does it for them. By code-sharing both UA and AC win. I don't think UA will add a YWG-DEN flight because it doesn't make sense to set up the necessary operations here. Yeah, AC would do most of it on contract for UA, but why would UA want to add any ticketing personnel or gate agents here for just one flight? They're better off concentrating on a few markets where they can have enough market share to make operations make sense, and let AC operate into the other airports where it has staff and facilities ready to go.
I think it is far more likely that AC frees up aircraft under the AC/CP consolidation so that they can add more on this route themselves.
A few questions. You say (at least on that AA ORD-YWG question, and KLM you said before, etc) that you have a friend who said these services would be starting. Just how credible is this friend as a source for this info? Also, when would these flights be announced? They don't just show up out of nowhere and start flying, the airlines do announce the start of service well in advance. If this stuff really happens, when will we actually hear about it?