WGN is available in over 65 million homes (which is more than TNT had when Nitro started or TNN had when they picked up ECW). 75% of those homes have WGN on channel 1-24, so the station is easy to find. It's a real sleeping giant of a network, and the Cubs still do great ratings for them.
If they're getting a primetime slot (or even a good slot as opposed to the afternoon crap), it'd be a great move. Not to mention Chicago is the natural place to center a promotion to compete with WWE.
There are also some very strong crossover opportunities with the Tribune newspapers (LA Times, Chicago Tribune and dozens of others) and the Tribune also owns TV stations all over the country (and part of the WB network). They're the fourth-largest media company in the US and produce quite a few TV shows as well.
The other thing is since WGN has little original programming, they run ads like crazy for what original programming they have. I saw a lot for some "Extreme Paintball" show that's starting in the *Fall* that airs on Saturday Mornings. They'll have a lot more support than they did at FSN.
I think the 8-10 EST slot on Mondays is open when they currently show movies and it would have minimal interference with sports.
Also, WGN channel 9 and WGN Superstation are different feeds sometimes. I could never watch that Blastoff show because in Chicago, there was just morning news on at the time. WGN should have the morning news nationwide, because they're funny in that "we can say whatever shit we want it doesn't really matter" way. They should carry more Cubs games. I don't care what they do with TNA.
Cute story, while we're talking about WGN: I was on the Bozo Show once, taped in November '94, aired February '95. I had to walk serpentine around a line of cones with a book on my head, which due to the shape of my head, I could not balance. I just held it there and handed it off to the other person on my team. Our team won the relay race. We won boxes of Matt's chocolate chip cookies and Little Mermaid hand-held games.