I realize this is an old topic but I have had this issue myself this week and the way I fixed it was by using a Data Rescue 3 which has an option in it called FileIQ where you can teach it to look for any file type. I loaded a couple of .mts samples in for it to learn the file type and then I was able to pull save all of the files I thought I had lost from a shoot earlier in the week.
i used Voltaic to convert the files which took ages but got the job done.