It is using about 120kB/s; around 110 more than usual.
As you can see repeating identifier of BC's channel.

Edit: Further debugging shown that BC's packets are send to all players; even to those in different dimensions.
Edit2: Destroying 32 lasers decreased it to 20kB/s for all players on server.

I'm not expert, but a pcap of the packets to and from the server might be nice.

Lasers are still causing big network overhead. About 80kB/s for 32 lasers.

https://www.dropbox.com/s/bdk3fzv14h2b4yq/bcspamdata1.pcapng?dl=0

Fixed too.

This reminds me that back in version 2 I think, the packets for pipes were being send to everyone, so if you went to the nether, at the same coordinates that a pipe network was in overworld, you could see energy/liquids/items traveling midair.