Yesterday I was driving through the Waterview tunnel after some minor accident in the tunnel. Signs were saying left lane blocked, keep right. As soon as we hit the tunnel my radio immediately switched to repeating announcement along the lines "This is control room. Tunnel is partially blocked, keep your safe distance". I went through few stations and it was announced on some of those frequencies as well. It got a bit annoying after about a minute with no way to turn it off (without turning off the radio). The second I left the tunnel it switched back to the normal radio.
How does it work? Do they just broadcast on major radio station frequencies in the tunnel in emergencies?
Side note: when I was entering the tunnel the left lane was closed (X above). They must have opened it while I was in the tunnel since there were cars coming through it. Immediately people from the right lanes started to push into the left lane even though changing lanes is prohibited in the tunnel. Typical!