These quotes appear contradictory, are they? If so, which quote takes precedence?
"Artillery Cannons (see tactical operations page 285) can also fire fuel air munitions.": Interstellar Operations, page 165.
"Artillery cannons may only use standard artillery munitions.": Tactical Operations, page 285.
The quotes appear contradictory, because fuel air munitions are not standard munitions; therefore, artillery cannons both can and cannot fire fuel air munitions.
Interstellar Operations is published after Tactical Operations. However, the contradictory sentence is part of an errata for T.O., and that errata was published after I.O.. I'm not sure if publication date is much help.