There is a White Paper posted on our internal site with information that you could review with your Cisco representative http://wwwin.cisco.com/voice/doc/ivr_eservices.pdf It describes the architecture and solution space. Vendors we explicitly tested against are listed with contact numbers. The solution uses the IP IVR eMail steps to send an eMail to a service provider who renders the fax and sends it to the fax machine.
The service provider takes the eMail with a text body and/or attachments in any file format (Word, Excel, Acrobat, etc) and they handle getting the contents to the fax machine in the correct format. The eMail address looks something like firstname.lastname@example.org.
Cisco IP IVR can e-fax as well as interface with a fax server that has a Simple Mail Transfer Protocol (SMTP) interface for sending faxes to analog fax machines. If a customer does not have a fax server, some service providers can provide the capability of receiving an e-mail and converting it to a fax (refer to the e-services white paper for more information on e-mail, e-fax, and e-page).
Hope it helps.