FAXcilitate would be the fax software for the PowerModem. Disregarding faxing for a moment, have you tried to use this modem for plain data communication?
Since this does not appear to be a soft-modem variant, it may be possible to use a normal terminal emulator (such as Terminal 2.2, FreeTerm, or even the communications section of ClarisWorks) without a special driver. Apple's Serial Tool 1.0.2 may also be needed. You could test this (once the terminal emulation software has been appropriately configured) by sending AT commands (like ATI, ATI1, ATI2, ATI3, ATI4, et cetera) to the modem.
If the FAXcilitate software is not available, would it possibly be worth checking whether another fax application can be used?
Yeah, I used ZTerm to play around with it, it responded to all the normal commands. I connected two PowerBook 180s together, and established a link to my PowerPort Gold.
I’m not sure if there was any other custom software for it back in the day, other than the fax package. If you install any version of Apple Remote Access it comes with the relevant scripts for this model.

