Originally Posted by
garycal
Thanks for the very complete answers. I apologize for the confusion in my first post -- I haven't yet booked a flight on Air Canada; I always book on United, with United flight numbers, regardless of whether the aircraft is UA metal or AC metal.
No need to apologize for being confused - it is a horribly confusing aspect of the MP program. I wish UA would follow the AA protocol that anything booked as an AA codeshare is always treated as an AA flight for mileage earning. Never a need to worry about this kind of stuff.
As for your specific question, I just went through that exact scenario a month ago or so. UA codeshared W fare on AC metal. I got a seat assignment (first sign that it was an AC mileage earning fare, as the ones that don't earn miles don't get seat assignments either) and the miles posted fine*. I was confused going into it too though, and I'm a 13 year 1K!
* - by fine I mean posted as an AC flight - so (as indicated by other posters), no elite bonus or MM/500 credit.