Re: WPC 10K Post Challenge - You Ready?!
To me the notification center should be accessible from anywhere in the phone not just the main screen even if it is deep inside the app space (except in full screen app (Games)). So this will be impossible if it is as a tile or a flick left in the start screen (both this case user have to come to start screen).
This leave us with the other options of pulling down from the top (mimicking droid) or do as @mmodimo has suggested in the post.
Wp8 already have a mini notification center which allows interacting with it even if we are in an app or even if the phone is locked. The volume control which pops out when the volume buttons are activated or pressed. Simply extend this to the notification center and everything will be fine even if the screen is locked. Lock button to wake the phone and volume button will get the notification (you can also make it read-only under lock screen) and any one of the volume buttons when the phone is unlocked (definitely clickable/touchable)