A few seconds with a search engine reveal the following information. They were both constructed in 1973 for Canadian National. Keewatin 2402 was formerly Keewatin 2400. She was originally numbered for the Canadian National as their 2501. In the late 80s, she was renumbered t0 3501. She was sold to Canac in 1997 and kept her number. Then she was sold to the St. Lawrence & Atlantic in 1999 where she again kept her number as 3501. She was sold to Hudson Bay Railway in 2004 and remained numbered as 3501. She was renumbered in 2007 when purchased by Keewatin to 2400. In 2008, the Keewatin renumbered her to 2402.
Keewatin 2401 was originally the 2512 for Canadian National. In the late 80s, she was renumbered along with her sisters into the 3500-3579 slot, recieving 3512 for her new number. She was acquired by the St. Lawrence & Atlantic (
No date and I'm unaware if she was purchased directly from CN, but I imagine the acquisition was in the same timeframe as her sister), keeping her number as 3512. She was sold to the Hudson Bay Railway in 2004 and kept her number as their 3512. She was sold to Keewatin in 2007 and renumbered to their 2401.
This information was primarily derived from the following link. So it appears to confirm the history for each unit that you've found.
http://www.cptdb.ca/index.php?showtopic=10453&hl=