In general, 8-hour shifts are more difficult to do than on-call. When you have an on-call duty, you might not get any call at all during the night. However, a shift means you have to be awake during the night which is really bad.
If you're limiting yourself to co-located teams, sure. US is UTC-8 through UTC-5. Add someone in the EU or South Africa and you cover with someone that's on UTC through UTC+2. Australia, Japan, and SE Asia include UTC+7 through UTC+10. If you're set up for international remote work (or satellite offices), you can get things set up so that someone's always on duty.
