While I'm sure the details are top secret, I think the existence of the monitoring has be known for quite some time. As I recall, a submarine disappeared much further away than the titanic wreck, much closer to Spain, and the recordings were eventually used to prove it was a collision of submarines or something like that. And rule out that the submarine was attacked by a torpedo.

So I haven't been following this story all that closely, but I would've been somewhat more surprised had there been an implosion or similar it wasn't sitting on a recording somewhere. How quick it is to extract, triangulate, etc are another story.