Jason is on the standards team in Microsoft, and he has a blog post discussing some of the moves to block Open XML at ISO coming from the anti-OpenXML movement (they even set up a 2,500 euro bounty on it):
I wasn’t involved in any of the discussions, but to me it’s not surprising that you’re seeing more people take an interest in Open XML going through ISO. There are already over 1,700 companies who’ve shown their support for Open XML at the http://www.openxmlcommunity.org site. It’s clear there are some people opposed to Open XML, but that shouldn’t be surprising, as you can never please everyone (it’s like the analogy I used earlier this week about trying to order pizza for a million people). Something you can’t argue with though is that Open XML documents are going to exist, most likely in large numbers as we move forward. Because of this, you see that there are a large number of businesses and individuals out there who have an interest in seeing the ISO take over the stewardship of Open XML.