OM & IS in CMA is Operations Management & Information Systems.in CMA Inter
In CA Final there is a subjectcalled Operation Research a section with Advanced Management Accounting ( widely known as Costing ) OR covers some part of OM Topics like Transportation/LPP/Assignment PERT & such topics, but it does not cover any Engineering & Production Planning & Production Process Topics as they are in OM of CMA.
IS of CMA is Covered in Full in CA Final Information Systems & Control Audit ( ISCA )
Suggestion is that dont attend CA based classes for CMA you will badly mess up yourself. Rather OM & IS are simple to understand. You can do it on self study from CMA Study Material & Past Papers & you will get through for the exams. IS is nothing to learn in any classes but is a Theoritical Subject, Yourself read it twice & you will be done with it.