Associate Professor Anil Samtani (Deputy Director of CAPTEL and Associate Professor of Law at NTU) answered my question and gave permission to publish his response in full:
Here's my take on your query. The porting process involves both linguistically translating the licenses (where applicable) and legally adapting them to particular jurisdictions.
So whilst CC does not and is unable to warrant that the localized licences will be enforceable, the idea is that the adaptation process will make it more likely that a local court will enforce the ported licence given the fact that the licence has been adapted to take into account the nuances of the local laws in the country concerned.
Having said that, though, the unported licences have also been couched using terms consistent with international intellectual property conventions and treaties so they are also crafted with a view to ensuring that courts are likely to enforce those licences.
Nevertheless, because of the differences in place in various copyright legislations the world over, it is hoped that the porting process will bring about greater certainty to creators and users in understanding their rights and obligations as the ported licences will take into account these legislative differences.
It is also probably worthwhile to note that the CC licences contain "severability" clauses -- meaning that, if a certain provision is found to be unenforeceable in a certain place, that provision and only that provision drops out of the license, leaving the rest of the agreement intact.
Thanks, Prof Anil.