The provisions of Appendix 1 to JAR-FCL 2.320E, which is where the (incorrect) assumption of 30hrs ground and 15hrs flight instruction comes from, will be replaced by Article 7(2) of the Regulation on Personnel Licensing, which states:
Applicants for Part–FCL licences already holding at least an equivalent licence, rating or certificate issued in accordance with Annex 1 to the Chicago Convention by a third country shall comply with all the requirements of Annex I to this Regulation, except that the requirements of course duration, number of lessons and specific training hours may be reduced.
The credit given to the applicant shall be determined by the Member State to which the pilot applies on the basis of a recommendation from an approved training organisation.
In practical terms, this means that you will have to approach an ATO for an assessment, based on which a recommendation will be made to the competent authority who may (or may not) give its approval. Every applicant should, therefore, be assessed individually, depending upon their experience and ability (and the ATO's wish to make a profit), and the blanket 15/30 will be consigned to the dustbin of history where it belongs. However, given the UK CAA's record of making up the rules as it goes along, usually in an effort to reduce its workload, I would not be surprised if, in the UK at least, it were left entirely to the ATO's to determine the credit awarded.