Excellent question!
In the ending cutscene in the 1985 Cold War
Crisis campaign's "After Montignac" mission , after Corporal David
Armstrong is captured by the resistance, one of his captors (Radim or Tomas)
says to him "The Everon Freedom Alliance has no quarrel with NATO".
Now, how you get from EFA (Everon Freedom Alliance) to FIA is beyond me. OFP
player Asger Wille-Jørgensen postulates that it stands for "Free Island
Alliance". My theory is that the vehicles are serviced by the local FIAT garage.
Got a better explanation? Tell me about it.