Actually, not really.
That is true about the track files that are converted in AutoChart Pro, yes, those are just autochart files with a bunch of lat/long/depth data.
However, the background map that is created from those data files, is actually basically just a background image that is georeferenced to show up in the correct location on the gps map of your depthfinder. The background map, actually doesn't contain any depth 'data'. Just an image of contour lines basically.
And one reason they don't let you copy the custom map from one card to another, probably has to do with concerns about copying cards and getting past the encryption on individual cards.