I wrote a few years ago about a Mystery At Otter Lake which involved two train locomotives that fell into the swamp at Turcot and are apparently still there somewhere. Here is a Gazette article from September 18, 1947 that seems to shed a bit of light on the whole thing – but no mention of the thousands of train wheels used as fill.
The article also implies that Lac Aux Loutres (Otter Lake) ran the entire length of Turcot Yards. Some maps show it as being a dominant spot on the island, and it also makes sense considering the nearby Lachine Canal is considered to have been built along a waterway used by Natives for centuries as a way of bypassing the Lachine Rapids. So, the mystery is not necessarily solved but this does give some credibility to the tale.