In a move that appears to solidify his role as a Viacom chief, Tom Freston restructured himself out of a job at MTV Networks, naming Judy McGrath to succeed him as chairman and CEO of the Viacom cable networks division. Freston was recently named to share the co-president and co-COO role at parent Viacom along with CBS chief Leslie Moonves. The two are seen as rivals and will eventually succeed Sumner Redstone as head of the company. McGrath was previously president of the MTV Networks Group. Mark Rosenthal, president and COO of MTV Networks, will leave.