What are the strength and firepower of Ivory X bombardments?
I don't own a copy of the rule book, it's 75$. The briefing you linked to says the following about the Ivory X Special Rules:


  Ivory X Special Rules
  
  You may purchase an Ivory X Staff Team for +25 points. Deploy the Ivory X Staff Team when you would deploy Independent Teams. 
  
  Anti-aircraft Artillery Platoons and Towed Tank Destroyer Platoons that have a Command team within 6”/15cm of the Ivory X Staff team can use it as a Staff Team to fire Bombardments. 
  
  Anti-aircraft Artillery Platoons and Towed Tank Destroyer Platoons that do not have a Command team within 6”/15cm of the Ivory X Staff Team cannot fire bombardments.
  
  A Bombardment controlled by Ivory X uses all of the American Artillery special rules on page 240 of the rulebook, except for Time On Target.


Without a copy of the rules, it is difficult to say if anything within the rules for American Artillery special rules contradicts what is in the linked briefing.

Luckily, you can gather from the rest of the briefing that the Ivory X bombardments can only be used to pin down enemy units. The historical accounts mention that Ivory X was able to pin down the enemy. This is also supported by the fact that all Ivory X bombardment rows of the chart show '-' for Rate of Fire, Anti-Tank, and Firepower.


  Ivory X provided the Indianhead Division with plenty of firepower in the form of .50 cal and 40mm anti-aircraft guns. Their harassing fire helped keep the Germans from moving freely through the outskirts and hills of Brest, allowing the Indianheads to easily move in and outflank the enemy.
  
  Firing Ivory X bombardments   40”/100cm - - -
  
  Firing Ivory X bombardments   48”/120cm - - -
  
  Firing Ivory X bombardments   64”/160cm - - -


The only thing that still confuses me a little about the rules, is regarding Towed Tank Destroyer Platoons. The rules mention that linked Ivory X Tank Destroyers are the only ones eligible to fire a bombardment and only using the Ivory X special rules. Rereading the above Ivory X Special Rules, would lead one to believe that you only have two possible answers to the question. My guess is that the answer is the former, but the use of the word "can" could mean that you have a choice of either pinning down enemies or firing bombardments as a Staff Team.

1) Use the 1 ROF, 2 Anti-Tank, 6 Firepower stats for Staff Team when firing bombardments.

2) Use the - ROF, - Anti-Tank, - Firepower stats for firing bombardments to pin down the enemy (cannot hurt them).


Staff team 16”/40cm 1 2 6 Automatic rifles, Moves as a Heavy Gun team
M18 Hellcat GMC Light Tank 2 0 0 .50 cal AA MG.
M1 76mm gun 32”/80cm 2 12 3+



  Towed Tank Destroyer Platoons that begin the game linked to Ivory X do not use the US Tank Destroyers special rules and only deploy the Tank Destroyer Section on the table.
  
  A Towed Tank Destroyer Platoon can only fire a bombardment using the Ivory X special rule.