I referred this issue to umpiring authority Rick Roder, who was extremely helpful and informative and also confirmed Andy's and my interpretation of the rules. Lacking a MLB Umpires Manual myself, I first asked if it was there.
This issue is not covered in the MLB Umpires Manual. I believe that most professional umpires would consider a ball that falls inside of the baselines between first/second and second/third to still be on the "infield" as far as this rule is concerned. Accordingly, this is how it is worded in the Jaksa/Roder manual:
It is a fair ball [2.00] if any portion of a batted ball (4) that is airborne falls onto fair territory beyond first, second, or third base.
The problem is that the rule was written referring to the typical batted ball going down one of the foul lines and without regard to the ball up the middle. I have seen misplayed fly balls on Astroturf fields that brought this problem to light; the ball had enough spin to propel it toward the foul lines. Of course, as it happens, the ball is picked up well before it has time to roll that far.
Next, I asked him about the nebulous qualification for balls hit to the outfield:
I also have an issue with this section of the definition: "A FAIR BALL is a batted ball…that is on or over fair territory when bounding to the outfield past first or third base ". Given that the outfield is defined as "the area of the playing field most distant from home base" [i.e. in the definition of OUTFIELDER, of all places], there's a lot of gray area there. Does that include the cutout areas around the bases? If so, then aren't the infielders stationed, usually, in the outfield, technically? What if the ball hits the cutout over a drawn in shortstop and goes foul in front of third, is it foul or fair? Logically, it should be fair, but I don't think the rules are conclusive.
Regarding "A FAIR BALL is a batted ball…that is on or over fair territory when bounding to the outfield past first or third base ".
The words "to the outfield" could have just as well been left out of the phrase; as you are finding out, those words only serve to confuse. Again, the wording in the Jaksa/Roder manual clearly defines how this rule is interpreted:
It is a fair ball [2.00] if any portion of a batted ball (2) is bounding on or over fair territory when passing any portion of first or third base.
Thus, the point at which the ground ball reaches the home-plate edge of first or third base is the key. At that point it must be ruled fair or foul by the umpire. The "outfield" really has no ramifications whatever in regard to fair/foul balls; the keys are the bases and when batted balls are going to go beyond the bases. Of course, there are issues in regard to the foul poles, etc., but these, as well, have nothing really to do with an accurate definition of "outfield."
Hope that helps. If you don't already have my manual, you might find it invaluable for deciphering how these things are interpreted by professional umpires. If you continue to rely on the wording in the Official Rules, you are destined to be continually frustrated. Believe me, I've been there!
Rick's manual seems a wise investment, and once I clear it with the mighty Mike's Baseball Rants budget department (i.e., my wife), I am going to pick me up one.