Yup, that's my understanding. You pay 25% tuition for a bit, and work 'in the field' somewhere. It sounds like most students work overseas, unless they have extensive international experience or are from another country, in which case they may be able to do work analyzing data they're already gathered (this sounds unlikely for most students).
I'll be doing the int health program (global disease epidemiology and control) and haven't decided whether to do a regular practicum or the Peace Corps Masters International program. With the latter, you finish your coursework, do the 3 months of cultural/language training with PC, and then serve as a volunteer somewhere for 2 years. You get a job placement based on your public health skills. Sounds like a great way to get a masters degree, field experience, and some more solid language skills... but that might be possible with just the practicum too. I guess I'll decide by talking to people who have done both.