I really don't have a clue on this one, but I wish I had! If you get any leads on it, keep us posted? I'm darn curious now!
From your description, I'm confident you can rule out Observatorio Nacional Brasileira, as you would've had ten-second interval voice IDs and pips. Italcable has a data burst at each minute, but they also play music, and would have had time announcements in Italian anyway. As for the USB thing... I really don't have a clue, but I wish I knew!