The article doesn't mention having to have an iPhone for Siri to be integrated into the car--that's the whole point! Not all BMW drivers necessarily own Apple products, and that's why Siri will be independently integrated into the car itself rather than you having to have a phone for it. This shouldn't be hard to do, really. I don't see why it would be "glitchy," because more so than not, it'll be better than any other voice recognition in cars currently available.
'11 6AT 335i xDrive ///M BMW PPK Stage 1