|I take it there is no software or online service that would allow this to work other than installing a new analog phone line?|
Not that I know of.
We have analog cards in our PBX here at work in order to provide lines for fax and modem (we still have a few people using those for various purposes up to and including our Telecom technician so she can dialin to her PBX........lol.
I would compare prices (analog card vs getting the telco to set you up with an analog line) and I would go with whichever is going to be the most cost effective.
Would a virtual modem work?
I highly doubt it. Virtual or otherwise, as far as I know a modem requires an analog line.......period, full stop.