At long last, Cablevision Systems Corp. shareholders approved the creation of a tracking stock tied to its Rainbow Media Group. With Chairman Charles Dolan controlling a majority of the shareholder votes, it's not as if the vote's outcome was ever in doubt. Investors will get half a Rainbow share for each Cablevision share they own. The tracking stock is tied to American Movie Classics, Bravo, The Independent Film Channel, WE: Women's Entertainment, MuchMusic USA and Rainbow Sports. The company's New York City properties-Radio City Music Hall, sports teams, Madison Square Garden arena-are excluded. Metro-Goldwyn-Mayer agreed to buy a 20% stake in Rainbow's entertainment networks for $825 million after an auction of the entire operation failed to attract high enough bids. Dolan has been contemplating a Rainbow tracking stock for five years.