A question for any LU electrical engineer

I'll try this here.
Please feel free to move to a more suitable place.

While traveling from Marylebone to Harrow I noted a newish cable route between the NR and LU tracks.

Three similar cables in triangular formation with metal clamps at each post bound together with two metal? bands between posts.

Is this a three phase delta circuit using individual cores?

Main question.
At greater intervals than the posts there are what appear to be small,open-ended pipes with tapered ends tie-wrapped to the top of the top cable.

What is the purpose of these?

Thanks

Andy