The voicemail capabilities are the same for a group mailbox and a personal mailbox. If the group mailbox is for a huntgroup you will probably want to provision a group mailbox monitor button on the phone(s) so you will know when there is a message. Alternatively, you can use the voicemail to e-mail function and e-mail the voicemail WAV file to multiple e-mail address targets.
When there is a group voicemail provisioned on a user's phone you may have to educate the end use how to look at the LCD display next to the line button to see if there is a message waiting on a shared extension vs. on the private user extension.
A hunt group extension is a virtual extension, it doesn't actually exist on anyone's phone. When you call the hunt group extension it will forward/fork the call to one or more real extensions either in sequence or simultaneously. While the huntgroup is a virtual extension, there is actually a real voicemailbox created for that extension. In order to monitor if there is a message for the huntgroup mailbox, we needed an intuitive way to do it so that it didn't interfere with other real extension based voicemail notifications. To do this we created a new button that monitors the group voicemail box (MWI) and also acts as a speed dial to retrieve messages from the group mailbox.