The SSCBS entrance test is open for both math's and non-math's students.
But being from a math's background is preferable as the entrance test requires decent knowledge of math's upto class 12. The reason for this is that the subjects studied under the courses BBS and BFIA require the understanding of math's topics of class 11 and 12, such as integration, differentiation, set theory, AP and GP, etc. at various stages. So, to avoid any problems in studies that a non-math's student might face, the college keeps the difficulty level of the mathematics section a little high in the entrance test, rather than desisting anybody from taking the test.
But yes, if you have a learning attitude and are ready to put in some extra effort into your preparation, then math's won't be a barrier on the road to SSCBS.

Edit: This answer was written before the University of Delhi had stated its guidelines for the 2015 batch. For the entrance of 2015, math's was a compulsory subject for admission in SSCBS and other colleges offering BMS and BBA(FIA) courses.

Hope you got the answer.