at my old university anyway, the difference between a BA & a BSc in math is the electives. a student can get a BSc from the faculty of science by doing the math requirements & science electives; or a BA from humanities by doing electives from humanities (philosophy, latin, greek, english etc), or a BA from social sciences by doing social science electives (econ, psych etc).
It varies from one college/university to another. Where I teach, some departments offer only the B.A., and others (like physics) offer only the B.S. There was once a difference in "general education" requirements: B.S. students had to take a certain amount of math, whereas B.A. students had to take a foreign language. Now, however, the general education requirements are the same for both degrees, so they're indistinguishable in practice.
Nevertheless, our psychology department still offers their students the option of getting either a B.A. or a B.S., with the same required courses!