Omniture SearchCenter version 2.2 ostensibly offers support for MSN AdCenter, but when you try to enable your AdCenter account you're asked for an API-Token which it turns out is only available by request from MSN (you won't find word of it in the AdCenter interface or even on Google).

I don't know yet how easy or hard it is to get one - the word is you have to have a sufficient monthly spend on MSN. BTW: This fact doesn't appear in the SearchCenter User Guide (v2) or the KnowledgeBase.