Not to quibble with someone who knows the rules way better than I do, but are you sure?
The section on p.196 seems pretty clear. Indirect Combat Spells that hit are resisted by Body + half Impact Armor + Counterspelling, but Elemental Indirect Combat Spells that hit are only resisted by Body + half Impact Armor. This would make sense to me, as the fire in a fireball is no different from the fire from an actual flamethrower, so jamming the mana around the target shouldn't make the blindest bit of difference to the damage.
The section on p.196 seems pretty clear. Indirect Combat Spells that hit are resisted by Body + half Impact Armor + Counterspelling, but Elemental Indirect Combat Spells that hit are only resisted by Body + half Impact Armor. This would make sense to me, as the fire in a fireball is no different from the fire from an actual flamethrower, so jamming the mana around the target shouldn't make the blindest bit of difference to the damage.
It is quite clear. SR4, 196, "If the spell hits, the target resist with Body + half Impact armor (+ Counterspelling, if available), with each hit reducing the Damage Value."
Counterspelling applies on the damage resistance test with indirect combat spells. Interestingly enough, because of how its worded, it might work on area indirect spells also, But I doubt it, as the characters weren't the target of the spell, the area was.
As far as how is a fireball's fire different from an actual flamethrowers? The actual flamethrower's fire comes from a pilot flame, and some flamable substance (gas, napalm, etc). Fireball comes from (you guessed it) MANA! So, jamming the mana should have an effect on the magically generated fire.
Frank: Can you clear up a couple of things?
1) Does counterspelling apply to indirect area spells, such as fireball? SR4, 173 decribes area spells as targetting "areas or points in space", affecting all the visible targets in the area. The Counterspelling descriptions on 175-176 say, "When a protected character is targetting with a spell, she rolls Counterspelling dice in addition to the appropriate attribute (Body or Willpower) for the resistance test." Since the spell targets the area, not the people, do they even get counterspelling at all? If so, then does a mage who is in the area a physical barrier is being cast around should get counterspelling against the barrier going up, right?