Code-sharing is an ideal way for airlines to extend their network even beyond their usual routes and it means faster transit times and cheaper flights for passengers. As an elite status member, you should be cautious whenever you see a code-shared flight, because it means that things are about to get tricky!
Will I get points/miles for code-shared flights?
Maybe. If your flight is code-shared with another member of the same alliance, you will get points for your flights. However, the number of points depends on either carrier. For oneworld, you mostly get points based on the marketing carrier, but for Star Alliance, you mostly get points for the operating carrier. For Star Alliance customers, this means that it is not possible to predict how many points you will get because your ticket will have the fare class of the marketing carrier, but the points will be determined by the fare class of the operating carrier that is not disclosed.
If the code-shared flight is on a non-alliance member but the marketing carrier is the one you have your status with, you will usually get points, but most likely just award points and no status-qualifying points, flights or segments.
If the code-shared flight has the code of another member airline but the operating carrier is not a member, you will most likely get nothing at all. One has to be extra careful with airlines that are owned by a member airline such as Jetstar, Vueling, Eurowings or Air Dolomiti. These typically give you nothing at all unless you have your frequent flyer membership with the airline that owns them (Qantas, British Airways/Iberia or Lufthansa in this case). However, it is best to check what Wikipedia says about such airlines because they might be so tightly connected to their parent company that they are actually part of the alliance and behave no differently from the parent airline. You can expect full points (tier and award) for companies such as Iberia Express (Iberia), Norra (Finnair), Cathay Dragon (Cathay Pacific) or American Eagle (American Airlines).
Will I get lounge access?
If you are on a code-shared flight where both the marketing carrier and the operating airline belong to the same alliance, the answer is yes. There is no way around it, you would be eligible for a lounge access even without code-sharing in this case.
If the marketing carrier is not in the alliance but the operating carrier is, then the answer is no. I have seen people trying to get into a lounge while flying an alliance member airline, but they have not gotten in because the ticket has a different carrier code. You should not expect any other airport priority services either.
If the marketing carrier is in the alliance but the operating carrier is not, the answer is a resounding maybe. This depends on many things such as how tight of a collaboration the two carriers have, but mostly you would get a lounge access if the lounge is operated by the marketing carrier. For example, Jetstar flights sold as Qantas will get you to a lounge in Sydney or Auckland. If the lounge is not operated by the marketing carrier, you will probably not get access. Also, it is important to remember a practical limitation. Last week, I saw a guy with a British Airways marketed ticket getting denied from a British Airways lounge even though he was flying in Business Class! The flight was operated by a non-oneworld airline, but the trick is that the flight was from another terminal, so no lounge access was granted. So, it is important to check the practicalities first too – will the non-alliance airline even fly from a terminal the marketing carrier has lounges in?
Conclusions
All in all, I avoid code-shared flights as much as possible. Always make sure that the operating carrier is the same as the marketing one, otherwise you might be in for some bad surprises. Once I got a lot of Finnair Plus points for an Iberia marketed and a British Airways operated flight, but that was the only pleasant surprise I have ever had with code-sharing.
