Australian mining giant BHP Billiton is preparing for a political battle as it proceeds with its $39 billion hostile bid for Potash Corp. of Saskatchewan, one of the world’s biggest suppliers of the potassium rich salt used in fertilizers. With Saskatchewan Premier Brad Wall expressing doubts about the desirability of letting the mining firm fall into foreign hands, BHP has hired three former advisors to Canadian prime ministers as lobbyists in anticipation of a political challenge to any successful bid. They are: Michael Coates, an advisor to Prime Minister Stephen Harper in the last three election campaigns, William Pristanski, an aide to former Conservative leader Brian Mulroney and Bruce Hartley, who formerly worked as an assistant to Jean Chretien. Among the province’s concerns is that BHP’s purchase would break up the marketing company for potash that represents Canadian producers to foreign buyers, leading to lower prices and, potentially, less government revenue through royalties. Any sale would need to be approved under the Investment Canada Act, which can block purchases that don’t demonstrate a “net benefit” to Canada. However, Ottawa has so far taken a non-interventionist approach to takeover deals involving big resource companies. In fact, the only time it has used its power to block a deal under the Act was when a U.S. firm tried to purchase the space and satellite division of MacDonald Dettwiler and Associates Ltd.