The decision to grant dispensation is not made by the Catholic Church, but it is done by the Diocese. There is no automatic dispensation for St. Patrick's Day. In my Diocese (Harrisburg) there is no general dispensation.

Whenever I attended the Friendly Sons of St. Patrick banquet on a Friday, the Bishop would grant dispensation for the attendees prior to the trditional meals of prime rib being served. There was never a blanket dispensation.

Two years ago I attended a St. Patrick's Day Party when the 17th fell on a Friday. The hostess, who is Catholic, forgot about Lent when she planned it. Reminded the afternoon of the party, she actually telephoned the Bishop's office, explaining that meat dishes had already been prepared for the occasion, and the Bishop granted a special dispensation, stating that meat may be consumed by the Catholic guests, but only inside the home and only between the dining hours of 7 to 9:30. He wanted to avoid a mistaken assumption that the guests were free to eat meat for the entire day, and that going back to pick at the corned beef and ham was stretching the dispensation beyond its intended purpose.