AS5601 doesn't mention anything about retrospective, either including or excluding.
It actually does, very clearly and concisely.
"1.5 COMPLIANCE
The requirements of this Standard shall be used in conjunction with, but do not take
precedence over, statutory regulations that may apply in any area. Where no requirement is
given, good practice shall apply. In a matter of uncertainty, advice should be sought. This
Standard applies to new installations, alterations and extensions commenced after its
publication date or the date of adoption by the relevant Technical Regulator. It does not
apply retrospectively to existing installations, but any repairs or modifications to existing
installations shall comply with the requirements of this Standard. "