On Mainpine site could not determine if it would be compatible with digital phone lines. Do you know if this would this be an issue? Thanks for your help in advance.
Most cable providers convert their digital phone lines back to analog. (E.g. Time Warner) They have designed these converters (ATA's) to work with fax machines as they know an overwhelming majority of their customers only have equipment to handle traditional POTS (analog) lines. We use Time Warner Digital Voice Unlimited Lines with our fax board and fax machine on the same line.
Using a Mainpine board would really be helpful, but if you are wanting to receive faxes on your Server's fax server, it can't be the same line as the one the Brother Fax is using or the incoming faxes won't know where to go. You would have to send on a different fax number that would show your actual fax number so that companies faxing you would always send you your fax number.
You can set the Brother to manual mode so that it won't auto answer and receive faxes. You can use it for walk up faxing on the same line. We do this with our canon, and I have also setup practices with faxboards and Brother (8480DN, 8XXX, etc.) with the same setup. Walk ups are typically one pagers. Larger ones we use the ScanSnap and send out the fax via the computer or we can fax directly from every computer with the MainPine too.