I'm using Firefox v23.0 on a Nexus 4 running Android 4.3. When I long press within the URL bar to copy a URL, the only popup option that appears is "PASTE." There is no option to cut or copy the URL text.
I actually went ahead and installed the Firefox Aurora build (pre-Beta), and I found that they have implemented the same copy and paste toolbar that is found in Chrome, so I guess all we have to do is wait a couple more releases and it'll be baked into the regular Firefox for Android browser. Your solution works well in the meantime for anyone who doesn't want to use Aurora, though. Thanks again!