When I was in Montreal in August 2009, I found the European land snail Cepaea nemoralis along a railroad passing thru the city. The little survey I did eventually got published in the journal Check List.
At that time I had some anecdotal evidence that Cepaea nemoralis was also present elsewhere in the city. Since then, my sister and niece, who live in Montreal, have sent pictures of snails from the Westmount district of Montreal. Here is a picture of Cepaea nemoralis my sister found in her garden a few days ago.
I am now convinced that Cepaea nemoralis has established itself in Montreal.