The only time I can see that T&M makes sense is when it is clear that bid risk is too great:
Extensive fishing in old work...
Projects way outside one's experience...
Tracking down and fixing broken underground circuits...
For them I go with a minimum fee, T&M and a worst case maximum fee.
Everything else is bid work; it's the only way that I can get my per-hour rates where they need to be.
I normally will not even bid a T&M ticket unless it's for an established account. It demands mutual trust.
