Last week, the Interior Department sent a letter to Cadiz Inc. that the company long had hoped to receive. For years, the renewable resource company had been trying to build a drinking-water pipeline between land it owned over an aquifer in the Mojave Desert and thirsty residents of Southern California. To help get the go-ahead from the federal government, it hired the law and lobbying firm Brownstein Hyatt Farber Schreck to help grease the wheels in Washington.