I looked through their bulleted list of features and you can already do all but one of the things listed (if you even consider eyes free a feature).
eyes free just means that the screen won't turn on when Siri is used from a recognized eyes free Bluetooth device. that sounds more like a DOT requirement and Apple CYA than an end-consumer desired feature. if you don't want to see your phone's screen leave it in your pocket or upside down in a dash compartment. the proximity sensor will take care of keeping the screen off and any power savings that might bring. I'm guessing that GM's press release was really about formally adding MyLink as a recognized eyes free device. Not sure whether that means an update to MyLink, to IOS6, or both.
What doesn't work is turn-by-turn voice instructions. Surprise, surprise... aaand cue the BringGo sales pitch...