Compared with MBAs, Masters have the advantage in PhD application due to the research background. So how can MBAs leverage the experience and knowlege they acquired in MBA education for PhD application?
Through other forums, I have known some MBA folks who are applying or applied to PhD programs. Some of them actually did some research work during their MBA, and used their research supervisors as one of their recommenders. There is one guy who chooses to stay in school to work on a research project, instead of doing an intership as most MBA students do. This can actually be used to demonstrate to the potential PhD ad committee his committement in research.
It also helps in the application process if your MBA is from a branded school and your GPA is high. Depending on the courses you take during your MBA, it can be used to show certain strengths too (e.g. quantitative skills, etc.)