The OP may not be from the US. He or she may have also realized that in some places mobile phones and land lines have distinct numbers (this is certainly the case in Israel where specific "area codes" are reserved for use by mobile phone companies) and may be wondering if the same extends to voice/fax.

As for your examples, they may or may not apply in his or her home country. When I first moved to Israel I was amazed at how differently the telcom services were bundled here than in the States where I grew up. Things that I thought were distinct (e.g. voice mail) were integrated into my phone services. Things that I thought were all-in-one required special flags to be placed on the account. Faxes send out an easily recognizable sound pattern - it is not at all unreasonable to think that in some countries, that signal will be transmitted only from certainly specially designated lines.

So in my opinion, better to ask than not. Somebody is probably paying a lot of money for this software. Perhaps you could help him/her out by guiding him/her in refining the question?

Best, beth
Former telcomm data analyst (many, many years ago)