Sharing a fax machine and voicemail on one line, a question

I'm trying to help someone who has an Ooma system for his home phone, and a multifunction printer with built-in fax capabilities.

He wants to be able to receive faxes to his fax machine on the same line he gets his voice calls with. I'm not sure this is possible to have the fax machine answer incoming calls if it is competing for the line with a voicemail system.

For example, if the Ooma is set to go to voicemail after 4 rings, and the fax machine is set to answer after 5 rings, how is an incoming fax ever going to reach the fax machine? If I set the fax incoming ring lower then the Ooma voicemail, then all incoming calls would go to the fax machine and never go to voicemail. Is that correct? The only way I can see this working is if the Ooma is somehow able to determine that an incoming call is fax, and not voice, I'm not sure that is possible.

Is there a way to do this without having to use a second line? Ooma has a service called Premier that costs $120/year and gives you a second line for the Ooma box, as well as things like distinctive ringtones. Any help is appreciated, thanks.

This may help. It appears as if the Ooma has a fax mode...

The only way I know of to be half-way reliable is to get one of these:
http://www.newegg.com/Product/Product.aspx?Item=N82E16825104009
and use an answering machine instead of voice mail.

Voice mail will always win in the battle to answer because it's resident in the service, before the call even reaches the house.

And BTW, many answering machines support remote message retrieval with a 4 digit code on the bottom of the unit, incase that's the next problem...

[wish] I so wish that VoIP providers would wise up and set a fail over to an unused second line port so that faxing would be easy to achieve. People want added value, not added cost. [/wish]