You can open any MainStage patch in Logic since MainStage and Logic both share the same software instruments and plugins.
To open a MainStage patch in Logic, make sure the patches are in the directory:
HD > Users > “Your User Name” > Music > Audio Music Apps > Patches > Instrument
Then in Logic X, with a software instrument track, open the Library area and select the patch from “User Patches”
You can also save channel strips if you prefer, and then add those to your project inside Logic. You will want to save them in the folder Audio Music Apps > Channel Strip Settings > Instrument and then you can pull them into either MainStage or Logic.
If the channel strip you'd like to save is an audio channel strip, you'll need to save it inside the folder Channel Strip Settings > Track Then, inside Logic, you'll go to User Channel Strip Settings > Track and then it will show those channel strips exported out of MainStage.