IBM has announced many semiconductor technology partnerships that have failed to bear fruit. That has been my experience. I may be wrong about this whole thing but what I can tell you is that the amount of wafers IBM needs for the servers is miniscule in comparison to mainstream semiconductor companies. It just would not be feasible to have an IBM specific process like TSMC does for Apple.
The Samsung/IBM collaboration is 20+ years in the making so it has had many incarnations. True, the Common Platform collaboration was a spectacular failure. IBM and GF also collaborated on a 7nm process that never made it into production and resulted in GF's pivot away from leading edge process technologies.
I will have to do more digging but I do know that IBM gets wafers from Samsung and it is not a specialized process. It is Samsung 7nm HP like everyone else uses. I have not heard about IBM using Samsung 5nm or 3nm.
I did read about an Intel/IBM relationship but know little about it. It would make much more sense for IBM to get wafers from Intel due to the stumbling of Samsung at 5nm, and 3nm and Intel's high performance expertise, but I do not see Intel licensing IBM process technology. It would be a clash of company cultures, a made for TV movie type of thing or maybe more like a Real Housewives of xxx realty TV type of thing.
And here is a rumor we can start right now: IBM is responsible for Samsung's problems at 5nm and 3nm.