Is there a definitive article or bulletin that states the security built into the reading pane in Outlook 2007 and newer? Thanks

What exactly you looking for? Scripts don't run in the Reading Pane and is therefor actually more secure than opening a message in its own window. Attachments can't be executed automatically either; It requires user interaction. The Junk E-mail Filter even catches Phishing Emails.

It's been this way for both since a big security update for Outlook 2000 and the Junk E-mail Filter since Outlook 2003 (anti-Phishing might have been an Outlook 2003 SP2 feature but definitely included in 2007. I don't think there is still a recent article which explicitly discusses the Reading Pane security as it has been pretty much a non-issue for over a decade now.