So for the early samples available with UE4 the workaround for running packaged OSX samples was to use -pak, e.g.
open -a UE4Game-Mac-Shipping.app --args ../../../RealisticRendering/RealisticRendering.uproject -pak
However this doesn’t seem to work with the new packaged samples ‘Card’ and ‘Reflections’.
Basically you end up getting:
Failed to open descriptor file '../../../Card/Card.uproject'