Yes, it’s possible to be registered an Applicant Member in both the MMP and MEBA. If you ship out with MEBA, then you would have to turn your MMP registration card back in, and vice versa. After your voyage is over, you can go back to both unions and re-register for work. By turning in both shipping cards you are prevented from building a “Killer card” while shipping in the other union. Once you become a full union member, you will be limited to that union.
My info is five years old, so I suggest you call each union for details. You may get conflicting stories. Over the years, MEBA & MMP have had ‘pass through’ agreements allowing selected MEBA mates to become MMP mates, but this is not what we are talking about. For example, I heard the Second Mate on the Maersk Alabama was a MEBA/MMP pass through mate.
Your question applys to ‘Duel applicant’ membersip, which is different as only MEBA members and not applicants can be accepted into ‘pass through’ program, which probably is closed anyway.
As mentioned above be sure to call. Who ever answers the phone at the union probably won’t know the process.
I will guarantee, they will ask the top union official present, “Hey, I got this ‘Jack Ass’ on the phone who wants’s to know if he can ship with both unions, can he do that?” Good Luck!