Note that MLB didn't let the public see the old QuesTec results: it was only after pitch-tracking through non-official sources became commonplace that MLB posted its Pitch f/x data. Furthermore, they've been exceptionally careful to prevent structuring the data in a way that would permit data-mining of umpire's strike zones for particular teams. Doing that is possible but labor-intensive.
When Pitch f/x results first became public there were mind-blowing games. Go back and check Ian Kennedy's MLB debut or some of Dice-K's early games for overwhelming evidence of umpire bias. Those two games were so bizarre in the pattern of umpire error that they were once-in-a-lifetime results, if they were by chance, not bias, meaning that over 162 games of 30 teams over 60 years, you'd expect such bias in play-calling only once. On the whole, error patterns are now less egregious, but there are still games and moments that stand out as biased. Certainly yesterday, when Danley made three mistakes in favor of Rivera in the critical 9th inning, it stood out. Overall, here are yesterday's pitch-calling errors:*
[table]Team Pitching | Balls called strikes | Strikes called balls | Net error
Yankees | 15 | 4 | 11
Red Sox | 8 | 10 | -2[/table]
Each mistake costs a team between .1 and .2 runs on average, depending upon several factors including the pitch count, the number of outs, and the runners on base. (The actual difference can range much higher, for instance with a mistaken called third strike with two outs and bases loaded, but the .1 to .2 range is almost always good, with .14 to .18 often capturing the net effect.) Danley made a difference probably ranging between 1.3 and 2.6 runs in favor of the Yankees yesterday. Even without consideration of the very close baserunning calls that went in favor of the Yankees, just the pitch calling was enough to swing this very close game.
My personal observation was that umpiring has shifted mid-season to favor the Yankees in many recent past seasons. Until 2008 we haven't had universal Pitch f/x, though, so it's been tough to say and tougher to prove. Likewise, if this were true, it's tough to say whether Bud Selig suggested it, the Yankees FO bribed the umpires, the umpires were largely Yankees fans, the umpires were subconsciously influenced by the Yankees fans yelling "Kill the ump," the umpires were bought by gamblers, or if other factors were at work.
Furthermore, in isolation, this pattern of missed calls is highly suggestive, but it's not statistically significant by itself. It sure is an interesting data point, though, especially given our past week of frustration.
* Graphic results from Brooks Baseball, adjusted for batters' heights, used for this post.