In the US according to the NEC the cables have to be listed as CM, CMX, CL2 or CL3 or any combination of each (dual listed). Listing has to be printed on the jacket.
I don't know of any thread relating to a fire started by "high gain audio cables", whatever that is. If someone finds it I would be happy to comment.
The low voltage and signal cable safety issue is related to what their composition will contribute to the spread of fire as well as the fire and smoke load itself should they be ignited by an external source. Heating of the cable due to excessive current is not a concern since if used according to code it would not be a factor.
-Hal
