As far as a USA PPL would be no problem changing with CASA. As for RAA all time is recognised and a pilot certificate criteria is in the ops manual is section 2-13 .
RA-Aus OPERATIONS MANUAL
Section 2.13-1 ISSUE 7 –OCTOBER 2014
SECTION 2.13
RECOGNISED FLIGHT TIME AND/OR QUALIFICATIONS
For the purpose of this manual recognised flight time is:
For gaining a Group A Pilot Certificate and associated Endorsements,
Ratings and Approvals:
(a) dual and pilot in command hours gained in obtaining and maintaining a CASA aeroplane, helicopter, gyroplane, airship licence or overseas equivalents or Australian Defence Forces wings standard, overseas equivalents, a GFA Glider Rating or overseas equivalents and endorsements, ratings and approvals associated with these qualifications; and
(b) dual and pilot in command hours gained in obtaining a CASA Recreational Pilot Licence and former equivalent or graduation from an Australian Defence Force basic pilot’s course, whatever called; or
©verified logbook entries of training undertaken towards the attainment of a Licence or Certificate with a recognised organisation; or
[*]For gaining a Group B or C or D or F Pilot Certificate and associated Endorsements, Ratings and Approvals:
(a) all dual and pilot in command hours flown when obtaining a Pilot Certificate with another RAAO, or equivalent overseas qualification and endorsement, rating and approval associated with these qualifications for the corresponding Aeroplane Group; or
(b)verified logbook entries of training undertaken towards the attainment of a Licence or Certificate with a recognised organisation.
[*]Notwithstanding Paragraphs 1 and 2 of this Section, the Operations Manager may disallow overseas qualifications without recourse.
[*]For the purpose of this manual recognised qualifications are validated Licences, Certificates, Endorsements, Ratings and Approvals and overseas equivalents from recognised NAAs and RAAOs.