The reference-tab export gives you EventAttackTier and EventAttackSubTier columns. If a row lacks those, the type is not exo-eligible.
The actual numeric costs are set in this block:
SetReferenceCost( EventAttackTier.Drone, EventAttackSubTier.Light, 1 );
SetReferenceCost( EventAttackTier.Drone, EventAttackSubTier.Medium, 2 );
SetReferenceCost( EventAttackTier.Drone, EventAttackSubTier.Heavy, 3 );
SetReferenceCost( EventAttackTier.Cutter, EventAttackSubTier.Light, 4 );
SetReferenceCost( EventAttackTier.Cutter, EventAttackSubTier.Medium, 6 );
SetReferenceCost( EventAttackTier.Cutter, EventAttackSubTier.Heavy, 8 );
SetReferenceCost( EventAttackTier.Corvette, EventAttackSubTier.Light, 16 );
SetReferenceCost( EventAttackTier.Corvette, EventAttackSubTier.Medium, 24 );
SetReferenceCost( EventAttackTier.Corvette, EventAttackSubTier.Heavy, 32 );
SetReferenceCost( EventAttackTier.Frigate, EventAttackSubTier.Light, 64 );
SetReferenceCost( EventAttackTier.Frigate, EventAttackSubTier.Medium, 96 );
SetReferenceCost( EventAttackTier.Frigate, EventAttackSubTier.Heavy, 128 );
SetReferenceCost( EventAttackTier.Destroyer, EventAttackSubTier.Light, 256 );
SetReferenceCost( EventAttackTier.Destroyer, EventAttackSubTier.Medium, 384 );
SetReferenceCost( EventAttackTier.Destroyer, EventAttackSubTier.Heavy, 512 );
SetReferenceCost( EventAttackTier.Cruiser, EventAttackSubTier.Light, 1024 );
SetReferenceCost( EventAttackTier.Cruiser, EventAttackSubTier.Medium, 1536 );
SetReferenceCost( EventAttackTier.Cruiser, EventAttackSubTier.Heavy, 2048 );
SetReferenceCost( EventAttackTier.Battleship, EventAttackSubTier.Light, 4096 );
SetReferenceCost( EventAttackTier.Battleship, EventAttackSubTier.Medium, 6144 );
SetReferenceCost( EventAttackTier.Battleship, EventAttackSubTier.Heavy, 8192 );
SetReferenceCost( EventAttackTier.Dreadnought, EventAttackSubTier.Light, 16384 );
SetReferenceCost( EventAttackTier.Dreadnought, EventAttackSubTier.Medium, 24576 );
SetReferenceCost( EventAttackTier.Dreadnought, EventAttackSubTier.Heavy, 32768 );
SetReferenceCost( EventAttackTier.Mauler, EventAttackSubTier.Light, 65536 );
SetReferenceCost( EventAttackTier.Mauler, EventAttackSubTier.Medium, 98304 );
SetReferenceCost( EventAttackTier.Mauler, EventAttackSubTier.Heavy, 131702 );
SetReferenceCost( EventAttackTier.Planetoid, EventAttackSubTier.Light, 262144 );
SetReferenceCost( EventAttackTier.Planetoid, EventAttackSubTier.Medium, 393216 );
SetReferenceCost( EventAttackTier.Planetoid, EventAttackSubTier.Heavy, 524288 );