It's a proper, permanent, three diff setup. None of that nonesense VW use where it's front wheel drive until it needs to be all wheel drive.
I've copied and pasted this:
"The ‘Alfa Q4’ system
The Alfa 159 also adopts an evolved version of the permanent 4x4 system with three differentials (with a Torsen C self-locking unit at the centre). The heart of this design is the ‘Alfa Romeo Q4 four-wheel drive’ system, which splits torque constantly and dynamically between the four wheels, reaching the highest levels of active safety and sportiness. The Torsen C self-locking differential sends drive torque 57% to the rear wheels and 43% to the front. The system also guarantees excellent traction in all grip conditions by automatically checking any slipping.
The torque split between the front and rear axles is modulated constantly by the Torsen C central differential on the basis of grip.
This feature harnesses sportiness to enhance active safety. Modulation is mechanical, continuous and gradual, to enhance the perception of optimal, enjoyable, easy driving. There are no gaps in the torque delivery. Where grip is concerned, the behaviour adapts gradually and smoothly to changing road conditions. This ‘mechanical’ control is backed up by electronic stability control, which boosts performance and safety margins, in line with the Alfa Romeo philosophy.
The car is the state of the art in technical terms and offers important advantages:
• Q4 permanent four-wheel drive with a Torsen C self-locking differential makes for better roadholding, entertaining driving and smooth responses. Other technological archetypes with electronically controlled joints do not achieve the optimal balance between understeer and oversteer or the smoothness that are innate in the Alfa 159, and translate into superb active safety.
• The torque split in favour of the rear axle makes driving even more entertaining, because the car is even easier to handle, without detracting in any way from stability during sudden lane changes on the motorway, or other emergency manoeuvres.
• The possibility of travelling safely when grip is poor without having to use electronics to split torque, enhancing the enjoyment of driving.
We could say that the Alfa 159 Sportwagon Q4 interprets four-wheel drive from the Alfa Romeo point of view: it is basically a ‘mechanical’ system enhanced by cutting-edge electronic technology to guarantee maximum comfort and entertainment, combined with superb performance and absolute safety."
I've also found that it can split the power between (72/28) and (22/78) front/rear.
Sounds good stuff!
Remember the V6 is now available in front wheel drive only, so remember to ask for Q4 on the order form!