I found one example on CodeProject that was implemented for (I believe) BTS 2006. It looks like it would work, and if nothing else, it's a reasonable implementation of the BTS Samples base adapter. I'm just wondering if there are any commercial adapter packs including a FAX adapter, or if anyone else here has run across a need to send facsimile data out of a BTS application, and how they chose to address the problem.
Part of me says I could simply write the fax TIFF and a small XML message to a folder (with address info etc.), then write an external service to do the faxing using the built-in fax system in Win2K3. That seems like another possible alternative, since it would put the responsibility for confirming availability of the fax hardware, monitoring the queue, fault handling etc. outside the BTS application.
Anyway, I'm open to thoughts and suggestions - thanks!