Probably you mean a heavily discounted variable teaser rate for the first 6 months?
From about mid 2008 lenders started to edge away from tracker mortgage products,falling interest rates and increased borrowing costs for Banks coupled with the fact 99% of Irish tracker mortgages did not have a collar built into them made the Banks realise they had screwed themselves royally...too late though,having said that there were a few Banks still doing them right up to the end of 2008 if I recollect correctly?
( a collar is a mechanism that stops a tracker mortgage tracking the ECB or Central Bank if the interest rate falls below say 2.5%.Collars would have been built into a lot of UK mortgages)