I suggest your incorrect assumption is believing that you can implement CMM or TMM. These are simply models of perceived organizational maturity.
Watts Humphreys who essentially founded the CMM has stated several times there is no quantifiable approach to measure any CMM level. The US military attempts to wrap some numbers around it, as do other organizations. However, Watts also stated that in order to get to the next level, organizations must realize they are at the preceeding level. Meaning, that before you get to level 2, you must be at level one.
I have been to a lot of sites who claim to be level 5 by some magical measures and hypothetical formulas; yet I have never witnessed an organization operating effectively at level 5 as described by the CMM.
The CMM and TMM are maturity models that help Quality Assurance (not quality control) professionals understand the relative process maturity of the overall business. They were never intended as singlular project models to be implemented at a granular level by individuals with little or ineffective influence upon the complete process.
Good post Bj. I'll add that I've read recently about companies at CMM5 who have found that it really doesn't mean anything to the bottom line. Basically the companies did extensive third party evaluations of the effectiveness and found they were no more effective at level 1 than level 5. Next model please SEI.
"Imagination is more valuable than knowledge." (AE)