U.S. put monitoring devices in Northwest Passage during Cold War era.

Canada is going to put new monitoring devices in part of the Northwest Passage. It is ironic that the last devices were placed there by the U.S. during the Cold War. Of course the U.S. refuses to recognise the Northwest Passage as Canadian waters. Will we be monitoring U.S. subs etc?
"One of the worst-kept secrets in Ottawa is that the U.S. put underwater listening devices in the Northwest Passage with Canadian assistance," he said.
The article is at CBC.