Google's John Mueller confirmed in a Google+ hangout last Tuesday that Google does use site wide or site authority to determine where new pages that have no page specific signals should rank in search.
John said this at the 4:49 mark into the video:
For the most part, we do try to understand the content and the context of the pages individually to show them properly in search. There are some things where we do look at a website overall though.
So for example, if you add a new page to a website and we've never seen that page before, we don't know what the content and context is there, then understanding what kind of a website this is helps us to better understand where we should kind of start with this new page in search.
So that's something where there's a bit of both when it comes to ranking. It's the pages individually, but also the site overall.
Here is the video embed:
To many this is not new, but always nice to have Google say it on the record.
Hat tip to +GlennGabe for spotting this.
Forum discussion at Google+.