No, there are some Piebalds with no white at all. There patterns definitely look "Pie-ish", though.

Also, there is no correlation between the amount of white from the sire/dam and their offspring. It's all a crapshoot.

Allison (Lillyorchid) is probably our resident Piebald expert, so I'm sure she can fill you in on any other questions or she could probably find out from Mr. Piebald himself.