I use GV so I have no need for the native voice mail, yet I keep getting voice mail notices that are from the GV call screening option("Please press 2 if you want to connect").
It's very ignoring and seems to drain my battery alot since the notices don't pop up right away(they seem to hang in the background) till I get 15 or so of them. Once I get them my battery draw goes to about 1% an hour but till I do it's like 5-10% an hour.
No they wouldn't, it would probably just ring indefinitely, or until VM decides to stop the call and say you're unavailable.
It rings the same number of rings as does regular voicemail, except the caller encounters a "voicemail box xxx has no voice mail set up" error message and then disconnects. I re-activated my voicemail after this