Forum Moderators: open
So, sourcing the CMS, customizing, maintaining it, etc. would be IT responsibilities (though they'd obviously be working with some requirements input from the marketing/communications departments).
Actually administering the content, designing the content, and (even) template design should probably remain in marketing.
IT people tend not to be the best designers...
I guess it depends on your concept of what a "webmaster" does.
-jlr1001