Circa 1996-98, I worked at a Baby Bell that tried to implement CMM, I think they were shooting for level 3. They bought "QMO" from that part of Bell Labs that declared independence as "Telcordia".

Absolute disaster. The whole of CMM emphasizes documentation and artifacts (more documents) over actually writing code. I think there was a "Personal Software Process" that Watts Humphreys advocated even individuals apply, which sucked all the fun out of writing any software. The Baby Bell got a lot of documentation at first, and then output slowed as the artifacts got harder and harder to produce. Very little code got written.