Haldex and Transverse Engines

[xRIEx]

In a couple of discussions about A3 against A4/A5/A6 etc quattros (and VWs/other VAG 4WD), it's been stated that the A3 has to have a Haldex system rather than a torsen centre diff because the engine is transverse rather than longitudinal. Why is that the case?

Mitsubishi used a transverse engine in the Evo but I assume they didn't use a Haldex system - what's the difference? How did they take the power off the gearbox for the rear axle?

[xRIEx]

I think previously I misunderstood what Haldex was; I thought it was a fluid coupling but from images it looks like a clutch pack - is that right?