Well, if the warranty doesn't say anything about not covering Vipers, I'm sure it'll cover a Challenger. It is after all just a retooled 300/Magnum/Charger platform with pretty much the same powertrain and everything else. The LY is a shortened LX - nothing special there.
They don't cover the SRT's 'cause they KNOW we're gonna beat the hell out of 'em. (As well we should!)
Jeff