I think I might have found my answer .. according to http://wiki.cyanogenmod.org/w/Install_CM_for_jfltevzw
This guide is for advanced users and does not come with support. It is provided as a means to install CyanogenMod. A working adb connection as well as adb being in your PATH is required for this guide and users should not proceed without this. Additionally, you must be on build I545VRUAMDK or this will not work. In fact, if you try to use this method on a newer revision, you will almost certainly brick your device. Seriously don't try it. Downgrading won't work either. If you've updated, a qfuse is already tripped and any attempt to downgrade will also result in a brick.
You can check what build you are on in System Settings > More > About phone > Baseband Version
Can anyone confirm this?