You mean the multi BBS-platform communication they did in the mid to late90s?  I was a member of CommNet but I was running Image BBS not C-Net. 

I think the for the most part it was the regular BBS-to-BBS message transfer protocols with some key hub boards running additional modules that did the  cross-connection/conversion to tie the other networks together (C-Net, Image, Color64 (iirc))  there 
were just a few very awesome developers working on it.

Most sysops didn't see any of the code it would have been the hub sysops.

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