Maya move joints mode

Hey all,
I am using Python to put a skin cluster in move joints mode, but I can’t query that flag so I can toggle the title on my button. When I toggle the state of mjm I don’t see any change in the dependency graph either. Does anyone know what is actually going on when mjm is on?

You could have a look here C:/Program Files/Autodesk/Maya2012/scripts/others/moveJointsMode.mel and see what they are doing.
m_moveJointsMode.kSkinningEnabled / Disabled might get you what you are after, but this is just me digging around, nothing tested or tried.