Having now tried it, the column is fitted with an adapter that increases the spline to the larger size used on the mk4 Golf etc. I test fitted a Passat B5.5 steering wheel. Not sure what to do with the airbag wiring and horn ring, but I guess a VW/Audi/Seat/Skoda wheel will have the same fittings. Looking at the OMP hub catalogue, it suggests that a Porsch 997 wheel is compatible, not that I can afford one. They cost more than the car ;-)
Just to add that the Passat wheel is at least an inch bigger radially which is too much for me, my legs and the existing wheel already want to share the same space. It is much nicer to hold as it's thicker. So if you are short and sit very low in the car, you might be OK.