The file in question is ~/Library/Preferences/Adobe Photoshop CS6 Settings/Actions Palette.psp for CS6. Change the version tag as appropriate. All of the Action Sets are stored in there.
You can use this script
http://ps-scripts.cvs.sourceforge.net/viewvc/ps-scripts/xtools/apps/Ac tionsPaletteToFiles.jsx
to read the psp file and write out .atn files for each Action Set.