I wonder if this is not that strange. The first 3 NL pitchers used in the game are former ALers (Halladay, Lee, Clippard). The first 4 hits by the AL were by former NLers (Adrian Gonzalez, Bautista, Josh Hamilton, and Adrian Beltre). The first two hits by the NL were by former ALers (Beltran and Berkman).
With free agency, maybe something like this has happened before. Here are the former NLers who played on the AL team:
Here are the former ALers who played on the NL team: