Honestly what is the enterprise these days? Internal apps are getting very quickly replaced by SaaS. Some of them are built on Node.js and many of them aren't. Most of the larger ones are built on a mix of technologies.
And so is the enterprise. You'll find it impossible to find a single Fortune 500 company with everything they do in one single stack. It just doesn't happen. Microsoft have Linux services and systems. Banks are a mish mash of multiple stacks.
They might have larger amounts of one stack than the other, but so what?
To answer your question: yes, enterprises are using node.js. Both directly and indirectly. It's not just fanboy technology. It works. We switched Craigslist from postfix to Haraka and they love it. Just one example but there are plenty out there.