Interesting the tunnel was never sealed off. Also, an alarm went off when the migrant came out on the Canadian side. Maybe it will get closed off now. Sarnia won't want to have someone else go through and make insurance or legal claims against the city.
The Canadian portal of the St. Clair River Tunnel in south Sarnia. On the left if the original tunnel, opened in 1891 and now closed.
Source: Man arrives in Canada through subterranean rail tunnel, seeks refuge in Sarnia - The Sarnia Journal