I am flying today on two separate tickets, YEG to YYC on Air Canada, and YYC-ORD-DCA on United, both award tickets fwiw. I'm happy to report that the agent at the YEG check in counter was able to check my bags through to DCA, no muss no fuss. She cheerfully accepted the request, tyoed in the connecting flight info, and said "let's see if the system lets me do this" and it did. I note that the UA flights were both AC codeshares, I'm not sure if that facilitated things. But whatever the reason I was pleasantly surprised. And it's nice to have a happy datapoint to report for once!