Most cases fall into cohorts, which should be treated the same way. It's complicated, but this is how I understand it:
In March 2006, Clause 3.2 was amended to say "At the end of a fixed term you will be offered a tracker at the then prevailing rate".
Cohort 1 - Before March 2006, Tracker rate specified in contract.
The contract did not say that they would get the tracker back at the end of a fixed term.
AIB argues that by fixing, they changed their contract, and so AIB is not restoring their trackers.
"If the letter of offer specifies the loan is a tracker with a margin of x% then surely this is what should apply at end of fixed term"
I think that this is your cohort. You will have to argue that the manner in which you fixed did not make it clear that you would lose your tracker.
Cohort 2 - After March 2006, Tracker rate specified in contract.
The contract said they would get the tracker rate back.
The contract specified the rate
They are getting their tracker back at the rate specified in the contract.
Cohort 3 - After March 2006, no tracker rate specified in contract. Came out of fixed rate before October 2008
The contract said that they would get the then prevailing tracker rate.
They were offered the tracker when their contracts expired. Most accepted it and so are on trackers.
Cohort 4 - After March 2006, no tracker rate specified in contract, came out of fixed rate after October 2008
They were not offered trackers on conclusion of the fixed rate as AIB were no longer doing trackers.
They are being offered them now at 3.67%.
AIB argues, that as this was higher than the SVR , they suffered no loss, and so are not part of the redress programme.
I don't think that AIB's arguments in Cohort 4 are defensible, and they are discussed here:
AIB restoring my tracker - but at 3.67%!
Brendan