None of the parties involved have commented on the report so far. We're asking the FBI if it can confirm any of the details. However, there's a real chance that CelleBrite might pull this off. Its forensics skills includephysically extracting the memory of locked iOS devices and examining the contents, so it might save the FBI a lot of trouble.
So why didn't the FBI turn to companies like CelleBrite before demanding that Apple write purposefully insecure software? There's no official explanation, but some suspect that the FBI was pretending to be naive in order to set a precedent -- if it could compel Apple to write software to get into one iPhone, it could routinely ask Apple to crack iPhones instead of turning to security experts. If so, the decision to ask CelleBrite for help may be an admission that this strategy wasn't going to work.