Don't know for sure. The sedan, it's a real project as the rear lid and tail lights are not compatible. But for the avant, the tailgate is the same, as is the bumper bar, and the tail lights are the same shape.
You might have to swap some supporting plastic. But I imagine you can find threads on retrofitting the facelift bumper on the avant with enough searching here, audiworld, and audi-sport.net.
B8.0:
https://audi.7zap.com/en/rdw/audi+a4.../8/807-807060/
B8.5 (they split it into two pages for B8.5 for whatever reason):
https://audi.7zap.com/en/usa/audi+a4.../8/807-807055/
https://audi.7zap.com/en/rdw/audi+a4.../8/807-807070/
the securing plate and the guide sections are the variables you might need to change over.
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