Hi,
ok, I see: two options:
create a fsm on the camera itself and create a global event "SET FOCAL TRANSFORM", from anywhere you like ( your prefab).
in your Fsm on that camera, then you can receive that global event, store the sender using the action "Get event info" and pick the "Sent by game object" property.
then you can use the action "set property" to set the transform to be the "Sent by game object". The trick however is to get the transform, not the gameobject as the focal script only accepts transforms, so you have to create a FsmObject or type transform and use the "get component" action to get to that.
this way you won't loose reference to the focal script cause you do that locally.
IF you don't want to do that locally, you will have to use the action "Find GameObject" and reference the tag "MainCamera" and use that to set the focal distance using "Set property" action.
I have attached the first variant, as it's nicer in my opinion. It requires Unity 4 Pro and Image Effects packages.
bye,
Jean