PT4 notes are stored in the database and will be transferred if you
Backup/Restore your database; or you can export/import notes separately using Database > Notes.
Player notes are specific to the player you took the note on though, so if you took notes on a Merge player and now you play at a different site those notes won't apply to any of the players at your new site.
If you mean NoteTracker note definitions instead of notes you took manually, then those will work fine between Mac and PC and when you play at different sites.