The score is not determined before the simulation is run. It is, however, determined before you see it "live".
The whole point of the Game Engine is to Calculate the Final Score between the two teams. So i agree with you that the score isn't predetermined because then that would make the GE pretty pointless (other then to read the Play-by-Play) but most of the time if can't watch a Game Live I just check the Box Score.
I wouldn't say it is "Determined" when you are watching it "live" however it has been "Calculated" thanks to the running of the GE.
Neeber
When the Beasts Roar all in the way shall be struck down!!!!!