In reply to a post by iwish:

This is what they was doing
Openreach
The cable was black

Pushing the fibre ducting through. They will blow the fibre at a later date.

If you mean that all they was doing is placing pipe so then can later pull the fibre cable then am not sure about that.
The cable was black and not overly thick and had some white writing on it
This is the very same looking cable Picture of cable

Most blown fibre tube will have a yellow stripe on it. I can't zoom in on the picture you have posted, to see what the white writing says.

In reply to a post by Zarjaz:

Most blown fibre tube will have a yellow stripe on it. I can't zoom in on the picture you have posted, to see what the white writing says.

I can't clean it up much but it does look like it says "Optical Cable" on it. Also it look like it's being pulled through a service tunnel because of the round manhole in the background.

The fibre optic they blow through is tiny so that tubing will be perfectly big enough inside to blow 8 fibres through it. That's not cable