To put things in perspective, everybody going to Jubilee will go to Rome. They'll probably go elsewhere but that will be randomly distributed across other areas of Italy and that random distribution will likely have a distance effect (closer - more impact, farther - less) and also a "touristy effect" (ie if the place is a big tourist draw - Florence, Venice, Amalfi...) it will get more of the secondary traffic. If you are in a low/no tourist area, the effect will be negligible.

ADDED: There is probably another effect that would drive traffic and that is a religious effect. If the area has a significant religious history (Shroud of Turin...) one could expect increased traffic.