I've finally been able to deal with my work phone's voicemail answering calls forwarded by Google Voice (can't adjust number of rings before it answers). This requires the GV plugin for Locale:
Cell near: Had to spend some time collecting enough cell sites around the tower I work in. Even then, I had to manually add a couple that popped up later. Ended up with 8 cell sites.Entry Task: Google Voice Settings, Configuration Work Phone On
Weekdays: Mon - Fri
Time: 7:00am - 4:00pm
Exit Task: Google Voice Settings, Configuration Work Phone Off
Works extremely well. Calls aren't forwarded to the work phone when I'm not near the office. I don't need to check the office voicemail if I don't answer a call and I'm not near the office.