I don't have AIBs response to hand but I believe one of their contentions was that the Letter of Offer did not mentioning a tracker so there could be no expectation of a tracker.
Which goes against this principal "contract term is plain and intelligible within the meaning of the UCTD" "For example, contract terms whose impact can only be understood when reading them jointly, should not be presented in such a way that their joint impact is obscured, e.g. through placing them in different parts of the contract"
Also in relation to the interpretation of the then Prevailing Rate from pg. 21
"Recital 20 Whereas contracts should be drafted in plain, intelligible language, the consumer should actually be given an opportunity to examine all the terms and, if in doubt, the interpretation most favourable to the consumer should prevail;"
This was quoted already but I believe that the phrase "then prevailing rate" fails the transparency test so is even more relevant.