Final answer:
The lumber producer in New Brunswick would support the railway for better market access, the stove manufacturing factory in Sarnia for efficient distribution and cost reduction, and even the United States Government might support it for enhanced trade and economic growth.
Step-by-step explanation:
The groups most likely to support the completion of the Intercolonial Railway would be those who stand to benefit economically or strategically from improved transportation and trade infrastructure. A lumber producer in New Brunswick would likely support the railway project because it would provide efficient access to broader markets for their timber products, facilitating easier and more cost-effective shipping to other parts of Canada and potentially to international markets. Similarly, a stove manufacturing factory in Sarnia, Canada West would welcome the railway as it would allow for improved distribution of their manufactured goods across the country and reduce transportation costs, enhancing their competitive edge domestically and potentially internationally. Despite the potential competition in North American markets, even the United States Government might see benefits in supporting such a railway to facilitate trade and economic growth across the border, both for American exporters and for industries dependent on Canadian raw materials.
From a historical perspective, after the civil war, the transcontinental railroad in the United States had fueled industrial expansion, including steel manufacturing, the development of the telephone, and the light bulb, and had a transformative effect on the nation's economic status and internal development. There is a parallel to be drawn with the Intercolonial Railway contributing to Canada's own industrial growth and economic prosperity.