Over many, many years of flying YYZ-LHR-DUB and YYZ-DUB-LHR and the inverse, I have never once been able to:

• Actually get a business fare on the EI segment, whether or not the flight is EI or AC coded.
• Select a seat, even with the EI PNR. Even via phone to EI with the EI PNR.
• Be able to get my EI boarding pass before landing at my connecting airport.

You can pay thousands for an AC J ticket and get the worst possible Y connecting experience on EI. You're the last to checkin, get a terrible seat, have to run to a transfer desk, etc.

It's a farce and has been so for many years. I hoped the switch to Amadeus fixed this, but seems not.