I stumbled across the fix for reviving automatic backups and keeping your USB UPS connected. In Terminal, enter the following:
Code:
sudo defaults write /Library/Preferences/com.apple.TimeMachine RequiresACPower -bool FALSE
Enter your administrator password when prompted, then reboot, and backups will resume.
This confirms that when the Mac is connected to a UPS, Time Machine improperly detects that the computer is on battery power.
This command also will allow backups to happen while the computer is actually running on battery power so once the bug is officially fixed, you'll probably want restore the default setting by entering the following in Terminal:
Code:
sudo defaults delete /Library/Preferences/com.apple.TimeMachine RequiresACPower