All plastics have melting points above the boiling point of water.
Central heating systems do not run at boiling point. A round
cross-section cable touching a round cross-section pipe wouldn't have a
large area of contact but the cable would have a large surface area with
which to dissipate heat.

Like I said before (and it seems nobody was taking a blind bit of
notice) in a lifetime of fixing aerials and dishes I never once saw this
problem.

Bill