AppleScript to read all notifications in the Notification Center OSX 10.10 Yosemite
I have not found a way for AppleScript to do this, but shell scripting has been effective for some people to get at the full database or log of past notifications.

Does the OS X log notifications from the Notification Center?


The format is an sqlite database, and it can be found inside this folder:
~/Library/Application Support/NotificationCenter


Assuming AppleScript is more important, you can call arbitrary shell scripts if needed from one, but other languages might be easier for database interactions / reporting.