Unfortunately, it's not clear how soon Windows in the Car might reach shipping vehicles, if at all. The crew in Redmond is testing code inside real cars and is comfortable with showing it to the public (see the source link's video at the 27-minute mark), so it's not just a pie-in-the-sky vision. However, the company also hasn't estimated availability or named car manufacturers that might be interested. While companies are working on MirrorLink-ready cars (Citroen, Honda, Toyota and VW) and head units (Alpine and Pioneer), that doesn't mean that you'll be controlling your Lumia with them as soon as they hit the streets. Given that CarPlay vehicles won't be available until later this year, it won't be surprising if any Windows in the Car implementations arrive sometime after that.