Re: "Variable vane" query...
As it was explained to me..
Basically, in a "normal" turbo, the vanes (the blade type things) are in a fixed position. When the exhaust gases run across the vanes, a specific pressure is required to turn the blades, this is only achieved when the engine has reached enough revs to generate the pressure, creating the typical "turbo-lag" which some love, some hate. With a varible-vane, each of the blades can rotate on its axis by a few degrees, this lowers the initial pressure required to spin the blades up, as the pressure increases the blades rotate into the stream to increase further the effeciency. This makes much more for a smoother power delivery across the rev range.
With regards to your other question, does your nearly 10 year old 156 have it, I'd have to guess no; VVT (not VVTi!) is relatively new to appear in road-cars, "to my knowledge" the cars currently using this tech are Porsche, Alfa/Fiat Group and BMW Group (I'm sure there are others now). I believe that only the current JTDm models have this (please flame me now!).