Can you just use and or have you tried the stock "clone" function within the BCT15? I would assume obviously you could clone between like models...BCT15 to BCT15, but may be worth a try between BCT15 and BCT15X??? Just a shot in the dark.
The BCT15 and BCT15X will not direct clone unfortunately, nor will the other "T" classic models to the new "XT" models due to subtle differences in Dynamic Memory Architecture. (Even the 396XT will not clone to the 996XT). The best method I've found it to use FreSCAN to copy from one radio type to another.