Isn't it common knowledge? 40% of employees work in companies with a worker council, it's pretty much the default for large enterprises.

I think it's pretty accurate regarding career effect. Worker Council members are generally much more union-involved, which employers obviously don't like too much. On the other hand: as long as you're a member of the worker council, you can essentially not get fired at all (short of being caught stealing or physically attacking people) so it's a stable career in itself, though rather like working for the government: you won't get to the highest heights, but you'll also not have to work too hard or fear for your job in an economic downturn.