After a series of delays, cost overruns, and legal challenges, the expanded Trans Mountain oil pipeline will open for business on May 1, the same-name state-owned company said this week. Trans Mountain has yet to obtain some approvals from the Canadian Energy Regulator, the company said. The expansion project sought to boost the capacity of the Trans Mountain pipe to 890,000 bpd. Oil producers welcomed the plan as they were expanding their output while markets for it remained limited to the U.S. Environmentalists, however, were very much not…