I have ridden a StreetStrider (inverted tilting delta) stand-up trike for several years. It has no tilt lock but it's pretty easy to balance at a stop, and it's extremely stable on wet, slippery surfaces. This and my experience riding my Sofrider leads me to believe that a tilt-lock may be unnecessary. My SS uses Sturmey-Archer drum brakes, BTW.
I see the biggest benefit of the TTrike being improved stability in rain on slippery surfaces (metal, wood, mud, etc.) that can cause the back wheel of a Cruzbike to slip out from under the rider. Better wet stability is really needed for Cruzbike commuting (since many cycle commuters frequently ride in rain). Another possible benefit is added cargo/passenger capacity--another need of urban transit cyclists.
Two questions for Jim:
-Do TTrike wheels eliminate the need for rear suspension?
-Might TTrike wheels eliminate the need for handlebars?
I ask the second question because I love to ride no-hands at speed because I can reliably steer with my legs, but it's hard to start and stop without the bars. If I had two wheels in back, however, it might make more sense to have under-seat handles (less weight, wind resistance in front).