It didn't show the game as blacked out when I signed in. Obviously I don't know if it's going to work yet, but it let me choose the WGN feed and brought up the player.
In happier news, the Phils just pulled ahead of the Brewers in the bottom of the 8th. 4-3 now, three outs for a single digit magic number! EDIT: Victorino three-run bomb. 7-3. LOL at Brewers pen.
The schedule grid on the Trib's sports page said TBD earlier. Now it says WGN. So it's looking promising. Otherwise, mlb.com has the game listed on the mlb.tv schedule for the day. But that doesn't answer whether it's WGN Chicago or national.