Recent news story about the Bryn Mawr program:
Some relevant excerpts:
“In a unique arrangement, students interested in geology at Haverford and Swarthmore colleges take the major at Bryn Mawr, so it’s always been coed.”
“Pedro Marenco is a paleontologist who does lots of outreach in Philadelphia schools.”
In practice, it is quite feasible for Haverford students to major in geology at Bryn Mawr, but I suspect that Swarthmore students rarely do the same. There are free buses to/from Swarthmore, but they take much longer than the bus to/from Haverford.