Originally Posted by
rehoult
It depends on what fare bucket the ticket booked into. If you book on United.com, and it places you in a Tango bucket (A, N, G, P, E) then you would get 25%. If it puts you into a Tango+ bucket (M, U, H, Q, V, W, S, L, K, T) then you would get 100%.
Mileage is credited based on the rules of the operating carrier, you can check Aeroplan.com for a list of what fare buckets count for each *A carrier.
The problem is that there really isn't any way to know what fare class on UA maps to what fare class on AC. People who work for AC can tell us for sure, otherwise you need to use KVS, EF, etc. and try and match up fares (but even that is an approximation).