Billionaire Hedge fund manager William Ackman's Pershing Square Capital Management said it owns a 12.2 percent stake in Canadian Pacific Railway.

CP's shares are undervalued and an attractive investment, and Pershing Square intends to engage in talks with the company's management, board and other stockholders, the fund said in a filing with the U.S. Securities and Exchange Commission.

Pershing Square owns about 20.7 million shares of the railroad company, the filing showed. CP currently has market value of about $10.5 billion, according to Thomson Reuters data.

CP is one of the least efficient railroads in North America based on key operating metrics and as a result is regarded by some analysts as a company ripe for a turnaround.

CP, Canada's No. 2 railway, started to show improvements in moving freight more efficiently and controlling costs a year ago but was then buffeted by a harsh winter of snowstorms and avalanches and an equally brutal spring of flooding.

Ackman, one of the industry's best known and most closely watched managers has made his reputation by sticking largely to U.S. stocks, including retailers like JC Penney and Target Corp. (Reuters)