Reg.9 PCR2015 (and art 9 Dir 2014/24) basically creates three specific rules. Firstly, it creates space for compliance with international law obligations, which can become more and more relevant in the immediate future as the EU exercises its external relations powers.
Secondly, it creates a specific criterion that money rules, so that procurement funded by international organisations or international funders is subjected to their procurement processes (this can, however, create difficulties in the integration of rules where the international organisation/funder relies on domestic procedures for all or part of the procurement process, which could create a spiral of cross-referrals).
Thirdly, it allows for negotiated solutions to mix-funded projects, where the international organisations/funders only provide part of the funds. In this case, it seems logical to require that the applicable rules are at least subjected to requirements of equivalence and effectiveness, so as to avoid infringement of general Treaty rules and the general principles of public procurement (see art 18 dir 2014/24 and reg. 18 PCR2015).
Finally, reg.9(4) PCR2015 (and art 9(3) dir 2014/24) introduces an (unnecessary) cross-referral to the rules applicable to defence and security procurement for those cases in which the specific "international" procurement concerns goods, works or services covered by the special rules (see reg.17 PCR2015 and art 17 dir 2014/24).
In my view, even if the 2014 rules now implemented by the PCR2015 have created some clarity (cf art 15 Dir 2004/18), there still seems to be room for clarification as to the concepts of "international organisation" or "international financing institution", as well for the introduction of a safeguard clause in case the procedures to be followed under other rules create a gap in scope of coverage or result in otherwise undesirable protectionism or direct award of contracts. However, these are issues that deserve separate analysis and do not affect the PCR2015 exclusively, so they are saved for some other time.