I heard through the grape vine it's going to be online co-op. Not sure if that means single player missions will be co-op or if it's more like horde mode in Gears of War 2 or firefight in Halo: ODST. Either way, hope it comes to PCs. Or maybe PC will get our own, exclusive mode.
Edit: oops, didn't look at the links your posted. After reading them, it sounds more like fighting off waves of enemy AI rather than doing single player missions.