The type of documents they produce in that [law] office, as in many other offices if not most I’m sure, is just pure text with a little formatting. They really have no reason to keep buying licenses for MS Office for this.
Now, disclaimer: this guy’s law firm is different than my firm. He says it is basically three lawyers plus some assistants; the firm I’m at this summer is around 1,000 lawyers with significant offices in the US, Europe, and Asia.1
So there is a bit of apples and oranges here, but… for better or for worse, what we do isn’t just ‘pure text with a little formatting’. That means we’re pretty deeply tied to Word. First, the tools around what we do are pretty sophisticated. The modern law firm has a suite of tools for document management. Among other things, these tools save all files to a central server automatically, provide revision control, automatically scrub documents to remove comments (albeit not always well), etc. These tools are not standalone- they integrate into Office.2 Second, it isn’t just ‘a little formatting’. Courts can be very picky- they’re perfectly happy to reject your documents if the margin or spacing is wrong. So, again, the tools are very important. Finally, time is quite literally money for lawyers- every moment usually counts. I don’t want to waste time thinking about formatting, and the client doesn’t want to pay me to waste that time either.
This isn’t to say you couldn’t replace Word. Obviously, some firms have done it, and many more will do so- not just for ODF, but also for markup languages or hosted software where no one ever sees a “file” in the old fashioned sense. But the switch isn’t nearly as easy as it might seem at first glance- lawyers often do fairly complicated things with text and are loathe to switch tools, often with good reason. So don’t expect that an overnight change is in the offing any more than you might expect all the vi users to switch to emacs tomorrow :)