March 1 (Reuters) - Oil producer MEG Energy said on Friday that line fill on Canada's long-delayed Trans Mountain oil pipeline expansion would start from April.

Line fill is the last step before the expanded Alberta-to-British Columbia pipeline begins service, providing additional access for Canadian oil to refineries on the U.S. West Coast and in Asia.

The Canadian government-owned pipeline corporation has called for 2.1 million barrels in April and the same amount of oil in May, CEO Derek Evans said on a post-earnings conference call.

For much of the last decade, oil companies in the world's No. 4 producing country have been forced to sell their barrels at a steep discount to global prices due to lack of pipeline capacity to export crude.

The project will transport extra 590,000 barrels per day (bpd) of crude, tripling the pipeline's existing shipping capacity to Canada's Pacific Coast once the C$30.9 billion ($22.79 billion) expansion comes in service, expected in the second quarter.

Trans Mountain did not immediately respond to a Reuters request for comment. ($1 = 1.3560 Canadian dollars) (Reporting by Sourasis Bose in Bengaluru; Editing by Maju Samuel)