Freddie Mac this week launched new MBS prefix codes for fixed-rate mortgage pools with less-than-normal servicing fee requirements, a market niche that has yet to gain much traction.Many mortgage bankers have pressed the secondary market to lower required minimum servicing fees that were established back when the MBS market was developed. Fannie and Freddie generally re-quire at least 25 basis points of servicing, but lenders say they could safely manage their servicing obli-gations and make a decent return for about half that much...