Thats the one valid point from the banks on trackers. The interbank funding rates in the credit crunch went off the charts and lost any correlation with the ecb rate. And that’s if you could get funds. So new business tracker mortgages became a non runner. Honoring commitments to your existing book was then the issue for banks and they tried every trick in the book to reduce those liabilities.
I don’t you’ll find interbank rates for a given period published anywhere but aibs annual reports for the period might shine a light