The software contains three new hardware identifiers, which are used to load the appropriate driver when a particular device is plugged in to a USB port on a Windows PC. Those identifiers all contain the cryptic string "Phone.Device." The identifiers for the original Zune devices are different, saying "Zune.Device."
This is the clearest evidence yet that Microsoft is planning some kind of Zune support for mobile phones. As I've been predicting for almost, this is not going to be a Microsoft-manufactured phone. Microsoft's not Apple, and it generally doesn't build hardware, although it might dictate hardware designs to a few select partners. Instead, I think these are three specific models of Windows Mobile 7 phones oriented toward consumers.
As I wrote, I believe the rumors that Microsoft is also planning a separate set of Windows Mobile interfaces and hardware reference designs for business users, and that these business phones might not come with the Zune media playback function.
I also believe the Windows Mobile media phones (or whatever they end up being called) are going to be different from the devices designed by Microsoft's Premium Mobile eXperiences (PMX) group, which will probably be successors to the Sidekick (Microsoft acquired Sidekick designer Danger in 2008), and will focus on social networking. I don't think those devices will feature a Zune client, Zune-like interface, or much music or video focus at all.
But we'll see in about three weeks, when the Mobile World Congress kicks off in Barcelona.