I can help answer some questions. I am a current MLT fellow.
At least for our year the minimum score that you must achieve on the GMAT is a 650. If you don't hit that then the program makes you get a tutor or take a prep class at your own expense.
The GMAT prep within the program is pretty minimal. You are really expected to be working on that on your own. I think one of the most useful aspects of the program, however, is the accountability. You have monthly check-ins and assignments that you review with your coach and there is a lot of pressure to actively work on improving your GMAT and other aspects of your application. I know personally it's very easy to lose sight of the big picture when you are swamped at work so I think this accountability is key.
If anyone has any more specific questions to ask me, feel free to ask here or PM me!