Download project workflow xml

I'm trying to reimplement RTC's work item state functionality on a custom client through REST, but I've hit a snag. I can get all the available states and all the defined actions for a project area. But given the current state of a work item, I can't figure out how to get the list of actions that are valid to be performed on it. What's the default location to either download the complete workflow (the XML or JSON representation of the Transitions table in the admin panel), or query a specific State for the list of Actions it will accept?