If you go to Google and search for 'intitle:"NBX NetSet"' , without the quotes, you turn up a few phone systems that have been indexed, some even in Michigan. This might be old news to some but still a bit surprising to me. It looks like newer versions of the 3com software automagically puts in a robots.txt entry for you.
If a new VxWorks/etc exploit comes out that affects port 80 on those call centers, I wouldn't want to be using those phones at the time. Good way to take a company offline unfortunately.