I also have the same question. I have asked before in the forums but no reply. I sent a message to the FoxFi people but never got a response. From what Ive read it does not work. Kinda defeats the purpose of paying for the FoxFi update then get JB pushed by the end of the year.
Update: I just started a thread under the Razr M forums. They got JB pushed to them so we will see if anyone replies. If so I will post it here.