The locations of the surface vertices are saved in the surface files (SCS coordinates):
https://neuroimage.usc.edu/brainstorm/Tutorials/ExploreAnatomy#On_the_hard_drive:_Surface
The other coordinates are computed from these SCS coordinates with the function cs_convert:
https://neuroimage.usc.edu/brainstorm/CoordinateSystems#Converting_between_coordinate_systems