I mentioned this in the RSCC thread, but I don't know if it's been mentioned previously but the RSCC's twitter feed (official?) says they have observed the Otters mating.
Hotwire is not necessarily 'fine', as some studies have suggested with some species that they are so aware of the proximity of hotwire that they avoid play-fighting or other behaviours within certain distances of the perimeter. Now we cannot possibly know of how the Smooth-coated otter responds behaviourally, or really have any useful reference point for model behaviour for captive individuals of this species, but it is worth bearing in mind that the restrictive nature of hotwire does not not just come from cominng into direct contact with it, and that its presence has the capacity to modify behaviours and use of enclosure space.
It's good that they have been mating, hopefully there are some appropriate cubbing facilities and potential separation enclosure should the male be aggressive.....