There is a requirement at ISO (or JTC1) for technologies in International Standards to be licensed at least under RAND term.
SC 34 (the committee on Document and Office Languages) has a long standing policy of not standardizing anything that is not free. Indeed, it also has a long running policy not to standardize any final (rather than "enabling") schemas itself: ISO HTML is the only exception I am aware of (but ISO HTML was made to allow certain governments and organization to specify HTML in contracts, not to become an alternative source to W3C.)
ODF and Open XML (assuming it is offered and accepted) are both technologies developed, proposed and driven from the outside. They are not SC34 products, nor does SC34 actually vote to accept them.
So if you are concerned about any intellectual property issues, please contact or lobby your national standards body: for US people, ANSI (INCITS) is the one. If you feel strongly, find out how to participate in your standards group. I am just a private citizen, paid by my company; it is a feature of SC34 that there are almost no professional advocates involved; people there actually uses the standards they maintain daily, and they work on the standards because the technology provides their bread and butter.
On the IP issue, I overheard one national body representative mention that he wanted clarification of this for the Open XML proposal, so I think you are on the same page as some people! I completely agree that IP issues are very important here: they certainly could constitute grounds which some organization might use to decide (if they must) between ODF and Open XML.
Actually, I asked sources close to the top of the XML tree at a large company with more than three letters last week. The answer that came back was that MS' license concerns is based on preventing someone from cloning MS Office from the user interface back. I suppose they see it like their programming APIs: they want (and in fact need to, for growth or maintenance of their business) to encourage Microsoft developers to use it.
We mustn't let the ODF sideshow obscure the probability that Open XML was not designed as a response to ODF; possibly going to ECMA and developing a community were (does it matter?), and certainly going to ISO was. But the central reason MS needs a properly documented publically-available XML format is to support all the third party Microsoft Developers. Document formats are easier to integrate with than APIs, in many cases. Forget WS-*, forget Windows Live, and even forget .NET; Microsoft really wants to put Office at the core of workflow systems, and Open XML is their strategy.