I can’t find it in the article, but I assume this is the same as all the other plastic eating organisms; They can eat plastic under specific circumstances, but would rather not. What is in the article; they can only survive on polystyrene if it is mixed with other food and nutrients.
Maybe we should be happy it doesn’t happen, breaking down all plastics which are currently everywhere would probably result in massive CO2 emissions. That’s why I’m always sceptical when these kind of articles appear; it gives some people an excuse to say the overuse of plastics isn’t an issue.