Of course, none of these points is definitive. Allen's landing site was determined by supposition, not by statements present in the source material, statements about distance are subject to error, the physical features of the site were imperfectly described by participants, and different meanings can be ascribed to the house associated with Allen's capture.
I thought, however, that the convergent evidence was good enough to risk suggesting the Ruisseau Migeon site, even though I admitted there were other statements about the battle site that I could not evaluate. These additional statements included that the stream was known by some as Ruisseau Truteau and that the battle was fought near Christie's farm.
This map shows several places referred to in this post. A - Montreal (where the British troops assembled before the battle), B - Ruisseau Migeon (English: Migeon Creek), C - Original site of a house linked with Ethan Allen's capture, D - Ruisseau des Soeurs (English: Nun's Creek), later called Molson’s Creek.
Since posting this information, a reader alerted me to two sources of information that greatly reduces the likelihood that Ruisseau Migeon was the site of the battle.
The first source of information is a letter dated October 23, 1775 from Grand-Vicar Montgolfier to Bishop Briand that states, in part (per his translation):
"Our city troop met them on the road to Longue Pointe, at a place named the Soeurs Creek, which forms the precise boundary between the two parishes,..."
If Montgolfier's information was accurate, then the battle was fought at a stream that was known as Ruisseau des Soeurs during the 18th Century and that in the 19th Century became known as Molson's Creek.
The second source of information is a couple of maps that show how land was divided among residents living near Ruisseau des Soeurs (Molson's Creek) during the first part of the 18th Century. (These were retrieved from an online photo album; the original place of publication is unknown). I cropped and combined these maps to create the image below (click to enlarge). The left panel map shows the stream in question. The right panel shows this site was associated with a Truteau family -- probably the family of Pierre Truteau and Marie-Charlotte Ménard, to judge from family history websites. Members of the Truteau (or Trutteau or Trudeau) family evidently continued to be a part of the Longue-Pointe community throughout the remainder of the 18th Century. Thus, there is good reason to believe that Ruisseau Truteau was another name for Ruisseau des Soeurs.
Below is an early 19th Century painting of this stream. If this is where the battle of Longue-Pointe was fought (as seems likely), then the British would have been advancing towards Allen along the road in the right foreground.