That's the advantage of n-tier systems. You keep your ancient databases, stick some business rules on top in Java and then talk to them from a bunch of clients that you can tweak as much as you like without worrying that you're going to break the important stuff.
Plenty of banks want to use agile, because they've heard it's cool, is said to deliver more better software faster, and is attractive to good coder job candidates. How far they are actually getting with it is another question.
