One more (potentially relevant) data point for you: years ago a friend had an early 2000s Litespeed. It was carbon/titanium/aluminum or some crazy combination like that. It broke. He had it crudely fixed and continued commuting on it.
I'm with Jed19 on this one. If I'm gonna buy a titanium frame, make it full titanium. I'd really like one with a titanium fork but I don't think I've ever seen one! I don't understand mixed material bikes. Make it full steel, full aluminum, full titanium, full carbon. The mixed ones just seem like marketing BS and are more failure prone at the joints.