CBS has raided the reportorial icebox over at ABC and signed Karen Burnes, one of the network's top investigative reporters, as correspondent on its news magazine "West 57th," it was announced Wednesday. Burnes, a correspondent for ABC's "World News Tonight" since 1984 and a producer with "20/20" before that, will begin "West 57th" duties in January. That's also when Jane Wallace, co-anchor of the CBS News show since its inception, leaves her post. Wallace reportedly was unhappy with the intense travel schedule her post required and decided not to renew her contract with the network. She is said to be a candidate for an anchor post on "USA Today," a news-feature magazine show set for syndication next September.