Prem Watsa’s Fairfax Financial Holdings Ltd. is in talks with the Ontario Municipal Employees Retirement System to see if the pension fund will help finance his $4.9 billion takeover of Allied World Assurance Co., according to a person familiar with the discussions. OMERS could take a minority stake in Zug, Switzerland-based Allied, and there have also been talks with other potential backers, said the person, who asked not to be identified discussing a confidential matter.