The Harvard Library Office for Scholarly Communication has released a draft of Converting Scholarly Journals to Open Access: A Review of Approaches and Experiences for comment.
Here's an excerpt:
This report identifies ways through which subscription-based scholarly journals have converted their publishing models to open access (OA). The major goal was to identify specific scenarios that have been used or proposed for transitioning subscription journals to OA so that these scenarios can provide options for others seeking to "flip" their journals to OA.