The sales were announced separately Tuesday by Borealis Infrastructure, the infrastructure investment arm of the OMERS pension plan, and by the Ontario Teachers Pension Plan.
A third partner, Kinder Morgan Energy Partners, a pipeline transportation and energy storage company and operator of the Express Pipeline, was also selling its stake.
The Express Pipeline System is a 2,763-kilometre crude oil pipeline system running from Hardisty, Alta., to Wood River, Ill, a major U.S. Midwest oil refining hub.
"Express Pipeline was one of our first significant capital investments and has been an excellent asset for Borealis since 2003," Borealis president and CEO Michael Rolland said. "It is a great example of our focus on creating long-term value for OMERS."
Rolland said Borealis was happy to be selling to an established U.S. and Canadian operator like Spectra and "excited about the potential to redeploy our capital in large-scale, global infrastructure assets."
The Express Pipeline System was also one of Teachers' earliest infrastructure investments, said Stephen Dowd, senior vice-president, infrastructure and timberland.
"We have had a positive relationship with our partners, Borealis and Kinder Morgan, and we will continue to look at future opportunities in the pipeline sector."
The transaction is expected to close in the second quarter of 2013.
OMERS is one of Canada's largest pension funds with net assets of more than $55 billion administered on behalf of some 420,000 members. Borealis has some $20 billion under management.
Teachers' Infrastructure Group currently manages an international portfolio of approximately $11 billion, including water and wastewater, electricity distribution, gas distribution, airports, power generation, high-speed rail, port facilities and timberland.
With more than $117.1 billion in assets, the Ontario Teachers' Pension Plan is the largest single-profession pension plan in Canada, investing the assets and administering the pensions of 300,000 active and retired teachers in the province.