Does escrow really work though? If the author of this software had placed a copy in escrow 25 years ago it is not clear to me that it would much use if the customer pulled it out in 2023 and tried to get it working. Access to the source, sure, but recreating the build chain on modern systems is not guaranteed to work at all. If someone told me they had escrowed 1998 vintage code and it was all mine to tinker with I would expect to find a CD with the release binaries, and a fat lump of a Visual SourceSafe database that expected NT4, some ancient C compiler (or worse, some VB5 runtime and a plethora of random DLLs) and who knows what level of deep magic to resurrect. And thats assuming I could even find hardware to run the OS of the build machine. Lord help you if there any kind of copy protection dongle nonsense going on, as was popular back then.
I don't work in that department so I can't tell you the exact process, but this is how it was explained to me: The goal of escrow is to have people not only understand the toolchain and ensure that they can get it working at the time when the software is put into escrow and then document it, but to also periodically pull it out of the archives and verify it can still be built. As part of escrow, steps are taken to ensure that any additional necessary software and hardware is kept to support this. That's what you're paying for with something like NCC's escrow service. If you want I can actually just ask my colleagues tomorrow.