I put 4 audio files in a stack: APE, MP3, AC3, and DTS of the same track.
I manually set the APE file as the top of stack (it defaulted to AC3, I guess by alpha).
Collapsed the stack and ran update tags from file.
It set everything (including the bit rate and file type) to the data from the APE track. I would expect the non-file specific tags to get updated this way, but was not expecting things like bit rate and file type to get replaced.
Expanding the stack and rerunning update library from tags set things mostly straight (except for the fact it changed the DTS file back to a 'data' file).