gabe:
Don't worry about the timing too much. In our case, we received two fines for one parking offence. We paid one fine at the time (still thinking the two fines were duplicates) and were surprised to be still summoned to court.
In fact, one fine was for an offence noted by a traffic warden (Local City Council) and the other was from a Garda. The timing of the two offences were 20 minutes apart. Apparently in this area, wardens no longer leave tickets on the window, so when the Garda came on the scene 20 minutes later, he thought he was first to nab us for the offence and left a ticket on the window.
Now that we are 1 month from the court date, we contacted the Garda, explained the situation and he is happy that because the time gap between the two offences is only 20 minutes, he is happy to treat them as one (fine already paid) and will have the case dropped in court. We don't need to show up.
Message: If you can explain your case to the prosecuting Garda or his Super, and you are lucky (like us) to be dealing with someone genuinely interested in saving us all unnecessary bother, your case can be pulled. So even if your letter to the Super takes time to process, don't worry in the meantime if a summons arrives in the post. Sometimes reason does apply.