Partly, but not seamlessly. Based on the shared experience, captions and keywords can be written to the files and seen by both apps, but Aperture ratings appear to be Aperture-specific and are not normally written out in a standard way that Photo Mechanic can read back. Color labels may have the same limitation.

If you want Photo Mechanic to see files already in Aperture, they need to be referenced files. A possible workflow is:

• keep images as referenced so both apps can access the masters
• use Aperture’s “write metadata to masters” for standard fields like captions/keywords
• use AppleScript or sidecar/XML-based scripting if you need to extract Aperture ratings

That means sharing ratings is possible only with extra scripting, not as a simple built-in sync. For JPEG+RAW managed together, it adds complexity rather than solving the metadata-sync problem.

So the practical answer is: standard metadata can be shared, but ratings/color labels are not reliably round-tripped between the two without custom scripting. Because of that, many people do initial ingest/culling in Photo Mechanic first, then bring selected files into Aperture for further work.