In general, all conversations with journalists are assumed to be on the record unless the interviewee specifically requests otherwise beforehand. The journalist should identify him or herself and explain what they are writing about. According the New York University’s journalism handbook, dealings of what can be attributed to a source, and what cannot, must be agreed upon before the interview – never after:
“A source can’t say something then claim it was ‘off the record.’ That’s too late. When dealing with individuals who are not experienced in talking with reporters, journalists should make sure ground rules and potential consequences are clear, and then perhaps offer leeway.”
In Ross’ case, some of the quotes about the rampant industry bid-rigging were from interviews in which she was first asking about her original story on snow plow safety. When she started interviewing about collusion, some people were willing to talk on the record at first, but later said that perhaps it would be best that they are quoted on background for their safety.