The following is a reasonably well-informed opinion based on working with some non-*A airlines on strategy and revenue management some years ago; however, I do not know the specifics of AC and *A, and how practices may have evolved.
In the good'ol'days, fares were published by IATA, a cartel of all the major airlines. There were no code-shares, no or very little fare discounting, and the price of a ticket was allocated to the operating carriers according to a formula, I believe largely dependent on mileage. Interestingly, it was considered too complex to do the calculations for all tickets, so a certain amount of random sampling was done to calculate for some tickets and extrapolate for the rest.
In the good'not'so'ol'days, after airlines were doing their own revenue management and competing on price, two types of code-sharing agreements developed. In a
blocked-space agreement, the operating carrier offered up X seats to the marketing carrier, and the marketing carrier did their own revenue management on that block (fares, booking classes, etc.) In a
free-sale agreement, the operating carrier controlled the booking classes and up-to-date availability, and the marketing carrier merely re-sold individual seats from that as available. The specifics of each bilateral agreement controlled the revenue-sharing. By and large the operating carrier got the lion's share of the revenue.
Layered on top of this, individual airlines began to enter
JVs on certain routes or markets, where they agreed on how to split revenues and costs, or profits, in that market. Generally, these were designed so as to make the economics
metal-independent, i.e. so the airlines didn't care if a given passenger flew on a ticket issued by airline X or Y, and on a flight operated by X or Y. These arrangements were then implemented via codeshares and routing/application rules in the pulished fares, plus a lot of wizardry on the accounting back end.
Finally,
alliance agreements included various frame agreements on code-sharing and JVs between members. These would provide frameworks where no specific pairwise agreements existed, but (usually? not sure) could be overriden by specific JV or code-sharing agreements where negotiated.
All this has generated a messy dog's breakfast. What I think it means is as follows:
- If a travel agent seeks to book a mixed ticket, different airlines' revenue management will be pinged depending on whether all-AC or mixed-*A flight numbers are being queried. In the mixed-*A case, each airline's RM is queried using the appropriate fare basis, with a mapping if needed. In the all-AC case, only AC's RM is queried, though on many (most? nearly all?) routes it will be interconnected on the back end and reflect the operating airline's data.
- If you use the AC web engine or call AC, it will preferentially serve up AC codeshares, and may or may not block non-codeshare flights. That probably varies depending on the phase of the moon and whatever quantum superposition principle applies inside AC's IT infrastructure at that moment
- FF benefits to the passenger depend (within *A) only on operating carrier, so it won't matter. Fare eligibility may, by design or by accident, vary, due to the interaction of complex fare rules and fare basis mapping between airlines. The most frequent source of inconsistencies are deep-discount premium class bookings, and mixed-class bookings with premier economy on some legs, since that is where the revenue management of different airlines differ the most.
- On the back end, the $ will be the same to AC where a JV exists, but may be different where that is not the case. There are a lot of unexpected surprises in sweating old IT systems like this and in a given situation, it's quite possible no-one has noticed.
Personally, on most of my tickets, the price and availability have been the same for using AC-codeshare flight numbers versus operating airline native flight numbers, though there have been a number of situations where using the native operating airline flight number, and doing a bit of a song and dance to get it, have paid off.