Can MS Fax or modem listen for tones if ans.machine picks up?

Config: WinXPproSP2, Fax Svcs (MS Fax Console), Broadcom V.92 56K modem,
Panasonic answering machine.

I'd like to have answering machine and MS Fax share 1 phone line. In order
for calls to reach ans.machine I believe it has to answer the call first.
Then I'd like MS Fax (or the modem?) to be listening to (eavesdropping on)
the beginning of the phone call and if it detects fax tones/signals from the
caller it would then intercept the call and take over, receiving the fax.

Is this a pipe dream or can this be done? If so, is it a function of the MS
Fax software or the modem? In either case, I don't see any obvious settings
that would enable this.

Note: The phone line connects from wall to modem to phone, so theoretically
if the PC/modem were to take over the call once it detects a fax, ideally it
would shut off the "output" to the answering machine so that the entire fax
call would not be recorded as a voice message, but that's a minor feature
that I could live without.

Thanks in advance for any advice!

-Rich

p.s. I realize that if I allowed the PC to handle fax and voicemail then
this might be easier, but for me there are several advantages to using my
phone's answering machine instead of using PC-based voicemail, so I want to
explore this first.