MTV Networks Thursday fired about 100 employees at levels up to VP in its music group and strategic services unit, sources said. The move was part of an effort to reshape the organization to handle more multiplatform activity, the sources said. More staff is expected to be added as the digital area ramps up next year. MTV is a company known for rarely firing staffers and the layoffs are said to be unrelated to the Viacom spinoff, which will put the MTV Networks in a new Viacom company separate from the new CBS Inc. A company spokesman had no comment.