TransCanada Corp said on Thursday it had filed for regulatory approval of its C$12 billion ($10.8 billion) Energy East pipeline, pushing ahead with a plan to ship oil sands crude to eastern Canadian refineries and Atlantic export ports. Canada’s No.2 pipeline operator said it had filed the formal project application with the National Energy Board, officially starting the clock on a regulatory review of the proposed 4,600 kilometer (2,860 mile) line. Energy East is TransCanada’s most ambitious project to date. The company, which is also the backer of the controversial Keystone XL project, wants to convert an existing natural-gas pipeline to carry 1.1 million barrels per day of crude as far as eastern Ontario, then add new pipe to Quebec and New Brunswick.