Interesting question, I don't know if I can answer but will try, I don't think you will need a separate cooper line. I do not use the standard AT&T as my phone provider. I am using our local Cable internet for internet and phone (Suddenlink). I do not have a VOIP system but do use the cable modem going to the regular phone lines in the building. I do not know enough about the technology of VOIP vs Old Wired systems to really tell you the difference. Maybe someone else can chime in.

As a side note, I recently replaced my Brother MFC and it still works as our fax. If you set it up with the old instructions on the board that Leslie wrote years ago I think you will be pleased. We use the Brother Drivers and software which seems to work well with this set up.