It appears that over wifi iTunes Radio is streamed at 256k AAC, but over cellular networks it drops to 96k.
Some of the posts here lament that, but I’ve been hoping that’s how it’s been all along. iTunes was supposedly going to have some kind of adaptive streaming for these very situations. I don’t want to unwillingly eat up my data plan because of iTunes Radio.
Even at 96k iTunes Radio should sound better than satellite radio.