In the (now closed) thread in the main forum it was suggested that this event might have been given a MTTH of 800 months to make it very rare that it should fire during a tournament but that the code for this (and other tournament based events) has not properly aborted the events once the tournament ends and this is why they fire at strange times.
Perhaps Paradox could consider whether this is a correct theory and, if so, whether this is indeed a bug or whether it was intended that these events might fire years after the tournament ends.