Well, thinking about how much TV companies here pay to get US shows six months after they first broadcast, to get to air them at the same time as the US networks you are going to need very very deep pockets!
It seems
the BBC is paying about $1m per episode for Heroes - for the right to broadcast it to a small portion of the world, months after it first airs and I don't think they have rights to broadcast anything other than previews online.
If you wanted to broadcast to a global audience at the same time as NBC... fuck.

But even for 2, 3.. 5 million per episode you'd be directly competing with them and it would also affect the resale value of the shows to other networks worldwide... I really doubt they'd go for it.
How would you finance it anyway? I can't see adsense etc really making that sort of cash! Attract the big guns and run commercials?