I had a passenger who was bumped from J to Y TLV to AMS on a revenue ticket (paid about $775 pp.) and this is the unedited email I received from the passenger (past end of Jan)
"Hey- they bumped us out of business to coach, but paid us $1100, gave us 3 seats in coach, and all the business class stuff (lounge, etc). What happened that pushed us out, and how do we know if it wont happen again?"
This was a couple, and it seems they were quite nice to them about it (like giving them an extra seat) besides for the comp offered immediately. So apparently it's very much YMMV (or YAMV - Your Attitude May Vary?), and likely QF booked passengers are treated as lower class citizens...