I've never heard of this. Granted BOI did raise finance through a dollar denominated bond issue (based on existing mortgage debt) and sold it to the Asian market. Don't think it was currency speculation on the bank's part but rather an acknowledgement of the preference among Asian financial institutions for products based in dollars.
Surely this exposes the mortgage holder to even greater risk? As you must now be concerned not just about the value of your house dropping but also the strength of the euro vs dollar.