They have a similar massed ride for the same purpose in my neck of the woods called the Chilly Willy ride which will happen in 5 days time and attract 800 bikes. If you are into tunnels try the three on the North Wales coast on the A55.
I worked as overnight fire crew in those tunnels a few years ago. When they had night time contraflow due to work in the tunnels. The contractor had to supply emergency teams in case of RTCs.
