UPDATE 1-Canadian Pacific says Paul Haggis elected chairman

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June 4 (Reuters) - Canadian Pacific Railway said Paul Haggis has been elected chairman, three weeks after a bitter proxy battle with New York activist shareholder William Ackman led to top level resignations at Canada's second-biggest railroad.

Last month, Chief Executive Fred Green and Chairman John Cleghorn both quit after a boardroom coup, a rarity in Canada's conservative corporate culture.

Ackman, whose fund Pershing Square is Canadian Pacific's largest shareholder with a 14 percent stake, had been campaigning since January to unseat Green, arguing that only new leadership could boost the railroad's operating efficiency.

In February, Pershing had added Haggis, a well-respected Canadian businessman, to its slate of nominees to sit on Canadian Pacific's board.

For a timeline on the proxy fight click:

Haggis was previously the president and chief executive of the Ontario Municipal Employees Retirement System (OMERS), and president and CEO of Alberta Treasury Branches, Canadian Pacific said in a statement on Monday.

He is currently chairman of the Alberta Enterprise Corporation as well as of C.A. Bancorp Inc, the company said. (Reporting by Jochelle Mendonca in Bangalore; Editing by Chris Gallagher)