I have a AT&T Merlin Legend at home to run our collection of vintage phones... similar situation that I haven't dealt with all these years later. Someday that card is liable to fail and take the "OS" with it. I have a second/spare card for it that I'll throw in a laptop and see if it's readable. We had Definity G3s at work back in the day but I wasn't able to haul that home. ;)
Merlin Legend should have the software "internal" to the Processor card, with the PCMCIA slot just used for doing backups or doing system upgrades. I believe some voice mail cards use PCMCIA cards as well, but the higher end ones went to notebook hard drives IIRC. Still worth it to back EVERYTHING up. I still have a hard drive I pulled from my Merlin Legend MAP40 Audix computer (It runs Unix with the voice mail system for Legend) and the ISA voice cards. I also have the floppy set from the 386 Xenix based Audix system that goes with the Legend as well. I need to archive it all and set it free. I've been looking for a Merlin Legend in the DC area for my friends for a while, so far none have turned up. Hope to load it with analog w/ ring gen cards for modems. - Ethan