I've asked this question in the FY+ forum in the past. The response was that the flight would need to be Marketed and Operated by a Oneworld Airline for Tier Points. So BA codeshares of EI fights wouldn't be expected to credit. This is no different to other airlines which partner outside of the alliance. You may get Avios, but not Tier Points. BAC treats EI different of course.

For this reason, I have avioded taking AA codeshare EI transatlantic flights from DUB to credit to AY+. If someone wants to test the water it would be interesting to confirm.