My daughter is an alum but she graduated 10 years ago so this information is not current. At the time there was a Brandeis-Wellesley orchestra but I don’t believe that there is cross-registration with any of the other schools. There was an upper level art history seminar at the MFA and each school including Brandeis could select 2 students to participate. That said many people attending Brandeis will have friends attending other schools in the area and I know that my d went to visit friends at Tufts and they visited her at Brandeis. Same with BU, MIT and Harvard.