http://www.stuff.co.nz/business/70732877/windows-10-uses-customers-computers-to-distribute-updates
I was not aware that this was occurring but for those of us on Data Caps it could be an issue
Check out this Microsoft Webpage
http://windows.microsoft.com/en-us/windows-10/windows-update-delivery-optimization-faq
Microsoft Update Delivery Optimization
Windows Update Delivery Optimization lets you get Windows updates and Windows Store apps from sources in addition to Microsoft. This can help you get updates and apps more quickly if you have a limited or unreliable Internet connection. And if you own more than one PC, it can reduce the amount of Internet bandwidth needed to keep all of your PCs up-to-date. Delivery Optimization also sends updates and apps from your PC to other PCs on your local network or PCs on the Internet.
I have changed my settings to send updates to other PC's on my local network only