Absolutely.
Some borrowers will try to do a DSA on their unsecured debts while not even talking to their mortgage lender. Of course, the unsecured creditors might well veto the DSA if they feel that the borrower should pay less in mortgage repayments and more to them.
What about a situation where there is in addition to the family home an investment. Let's say AIB writes down the mortgage. Ulster knows about this, and lets the investor continue on interest only. 10 years time. Family now has equity of 300K in family home, they've made excellent headway in paying off home loan and threw an inheritence at it, and property prices have risen etc. Now Ulster says we want full repayments, as per your loan. Borrower cannot afford it, so will be forced to sell family home. Is that a crazy scenario.