The Globe and Mail reports in its Friday, June 8, edition that BP is blasting Enbridge's abrupt reversal to the way it manages bookings on its mainline pipeline in a sign of growing tension over industry export constraints. The Globe's Jeff Lewis writes that Enbridge gave notice May 24 that it would require shippers to show proof of volumes for extra capacity on the key pipeline system, in hopes of curbing overbookings that have played a role in the deep discounting of Canadian crude prices. However, it scrapped the proposed change 11 days later on June 4 after customers, including large refineries in the United States Midwest and trading houses, balked at the new methodology for figuring how much oil they can nominate for delivery each month. BP, in a grievance filed with the National Energy Board, slammed Enbridge for overhauling the rules during a trading window in which crude oil is bought and sold and deliveries to refineries are scheduled. "Changing pipeline procedure in the trading period is simply unreasonable ... and could cause unintended consequences which could materially harm shippers," Jennifer Geggie, BP's vice-president of global oil for the Americas, said in the letter dated June 6.