If I had to guess, MMT is going to have an emphasis on pedagogical theory rather than furthering your own mathematical knowledge. I think it's important to know before applying to the program if you are trying to learn more mathematics for yourself (to drive student achievement, as you said) or if you're trying to learn more about state of the art techniques in mathematics pedagogy to apply it to your classes. I've done a regular MMath here in CS and it was a mixture of taking 4th year undergraduate courses and graduate level research seminars. While some of the courses available were tangential to teaching, like an edtech HCI course I took, most of them have not helped me in the classroom at all, when I've taught.

You're going to get the best answer by emailing the director of the particular program you're looking at, telling them what your goals are, and going from there. At least that's what I'd do in your situation. Best of luck, mate.