Some organized post-bacc programs have linkage progams, which allow students to apply before they complete their second year of post-bacc (and before the MCAT) to one medical school. It's kind of like early decision. Then they are given conditional acceptance, provided they complete their remaining coursework and score resonably well on the MCAT (often ~27). These programs have the advantage of cutting out the lag year for post-baccs. The disadvantage is that they applicant does not get to choose from as many schools as they might have through the regular application process. As locitamd mentioned, Brown has linkage arrangements with two post-bacc progams, Bryn Mawr and Columbia. Columbia has at least five other schools that it links with. At least in the case of Columbia, I believe that you have to do your entire post-bacc at Columbia through their formal program to be considered for these linkage programs.
BTW P&S does not have linkage arrangement with Columbia post-bacc.