The claim originated from Justin Hockings on the Siren Enthusiasts Facebook group. Seeing as the photo is from a distance, and there aren't any high quality images of the siren available, I can't personally confirm that it really is a Cosgrave. As such, the Wiki does not claim it to be one for sure.
https://imgur.com/a/HOWOjKs
https://imgur.com/a/YtpcqUq
While it certainly bears some resemblance, the image is very blurry and it could very well be a siren from a different brand entirely.