A couple of weeks ago Virgin changed an upcoming business class flight in August. The BNE - HBA leg was cancelled of a TSV-BNE-HBA flight.
When I rang (as the alternative offered flight did not work), the CSA eventually worked out an option that did work. I took the new flight, then she asked me for seat selections. She also said to check-in immediately at 48 hours plus get to the airport 3 hours early. After I had selected seats and it was all reticketed, I asked her why the seat selection etc as I had never had that offered on the phone before.
The answer - my two seats were actually overbooked in Business, but because all passengers hadn't selected seats, they would be bounced first as long as I checked in etc early.
PS - Our plans have all changed since because of other cancelled VA flights last week - I couldn't cope with the stress of going through it all again so TSV came off the agenda and someone got their business class seats back