Knowing the shortage situation of P-III, if they have them in stock now, they are most likely be cB0.
Many retail cB0 chips currently available are made in week 16 or so and packed in late May. So unless buy.com has had the chips in stock for quite sometime, you will have a good chance of getting cB0.
You have a better chance getting cB0 with OEM chips as they do not go through the process of being packaged.