It does not apply if an aircraft system failure occurs in flight affecting the landing performance. In this case you have to use the actual landing distance. You do not divide it by 0.6 in this situation. (According to Airbus 320 and 340 FCOM )
So technical diversion applies (you do not need to be in an emergency) but for commercial, fuel and wx case I can not say anything either.
But anyway, I think in all these cases excpet an emergency you most probably divert to an airport which is one of your operating areodromes within your company and which means the aeroports have been checked for the Jar regulation of required landing distance.
Hope it helps