The preference keyword.enabled allows you to turn off searching in the URL bar so it is just used for URLs (helpful in environments that aren't connected to the general internet).

When you do this, our place holder still says "Search with Google or enter address"

It shouldn't have Google in there.

well, you can still search using one-off buttons or search suggestions...

There are preferences to remove all of those as well :)

browser.urlbar.oneOffSearches
browser.search.suggest.enabled

_setURLBarPlaceholder can just be made to take the default if keyword.enabled is false. (It will still say search, but at least it won't be Google)

Because keyword.enabled is not exposed in preferences, I don't think this is critical. sure if we expose that pref through policies, then I can see it's an enterprise bug. I'd take a patch for it.