I see, I will take a look.
Any comments on why I can use DRM protected content on my phone using a non-Zune pass account?
Yes, when you sync with Zune, the Zune DRM key & activation process are handled by the Zune desktop software - i.e., your phone registers itself with the software, it handles the keys & entitlement process, at which point your Zune part of the phone is registered to a specific Live ID. The Live ID used to log into the phone is, at this point, irrelevant to the Zune app. Think of it as two different ways of activation, or maybe an override - by default, it'll try to use the Live ID you have on your phone (say, for instance, you get your phone, set it up with a Live ID & never plug into a PC) - but if the Zune desktop software overrides that, you can use a different Live ID for Zune Pass.
We tried this route with our phones (my wife & I), but it became too much of a pain. The $145/year each (we're on the old plan) is well worth it with how much we both listen to music.
Lastly - there have been rumors of new plans once the transition to Xbox Music comes about - a 'family plan' similar to Live Gold family is one of the top requests.