Originally Posted By: sn00p
I've always wondered (and googled, albeit not that in-depth) whether Mac OS is smart enough to know that your internet is being provided by a mobile network and therefore to not download software updates in the background (as mine is set to do) - I always thought that was a sure fire way to end up confused as to why all your data has gone.

OS X won't know what network it's on as far as limited vs unlimited. You can turn off auto downloading, so you just get a prompt to then download when updates are out.

Apple Menu - System Preferences - Software Update - uncheck "Download updates automatically"