The overwhelming majority of freight railroads in North America, including CP, are privately owned and operate on tracks that are owned, built, and maintained by the railroads themselves. At the same time, we are all subject to a number of regulations, guidelines and standards established and monitored by federal agencies such as:
Transport Canada
With 48,000 kilometres of track, Canada has one of the largest rail networks in the world. Transport Canada regulations, standards and programs work help make our railway system safe, secure, accessible, competitive and more environmentally responsible.
Transport Canada is primarily responsible for enforcing rail safety regulation (primarily the Canadian Railway Safety Act) and conducting research and development in support of improved railroad safety.
https://www.tc.gc.ca/en/services/rail.html
The U.S. Federal Railroad Administration (FRA)
The Federal Railroad Administration (FRA) promotes safe, environmentally sound, successful railroad transportation.
Rail safety regulation (primarily the Title 49 Transportation of the Code of Federal Regulations) is enforced by the Federal Railroad Administration (FRA). This agency also works closely with the railroad industry on various safety issues through its Rail Safety Advisory Committee.
http://www.fra.dot.gov