On September 1, 2011, TransCanada PipeLines Limited (TransCanada); NOVA Gas Transmission Ltd. (NGTL), a wholly owned subsidiary of TransCanada; and Foothills Pipe Lines Ltd. (Foothills), a wholly owned subsidiary of TransCanada, applied to the NEB for approval to implement a proposed restructuring of services and tolling on the TransCanada Mainline pipeline system (Mainline), the TransCanada Alberta System, and the TransCanada Foothills System. TransCanada also asked the NEB to approve final tolls for transportation services on the Mainline for 2012 and 2013. The application was stated to be a response to "recent and dramatic" changes in the supply, demand, and transportation markets of natural gas in North America. See TransCanada PipeLines Ltd., "Business and Services Restructuring and Mainline 2012-2013 Tolls Application" (Sept. 1, 2011). Published in the Canada – Oil & Gas section of the Rocky Mountain Mineral Law Foundation's Mineral Law Newsletter, Volume 28, Number 4, 2011.