VideoGamer.com has word from Gearbox Software on plans for a Brothers In Arms: Hell's Highway demo (thanks Gamer's Hell). The game is currently expected this August (story), but Gearbox president Randy Pitchford is not sure if the demo will be released before or after the game:

Yeah we do have plans for a demo. We haven't actually specifically decided which thing, which bit of the gameplay we're going to put in the demo yet. We're going to do it. I don't know if it will come out before the launch or not. It might not, it might come after. We'll see. But we're going to give a demo, because there are some people who really want to check things out before they buy.