AMT is Avid Media Toolkit that allows third parties to create native MXF wrapped essence. This, combined with a DNxHD license, gives them the ability to create native MXF/DNxHD. It also has the ability to create an AAF of the resulting clip.
AMT does not create the ALE. ALE is created by the manufacturers creating the files whether they use AMT or not. This is why you will find some inconsistencies between programs as to how and where metadata is stored.
Typically, AMT creating MXF/DNxHD will only have limited metadata – it puts the filename as Tape and primary timecode (typically TOD) into START. All other metadata is usually provided via the ALE as a merge or as you have noted, as an import/relink.
Personally, if there is an AAF created, I will:
1. Copy MXF files to Avid MediaFiles folder
2. Drag and drop AAF files into bin. These will relink automatically to media
3. Merge ALE into existing master clips.
I have seen instances where just importing an ALE and relinking has been very hit and miss with the ability to stay linked – especially with audio tracks. MOS clips seem to fare better. Some people have never had a problem –
Michael