Almost every magnetic ballast you find in the aquarium world is probe start.
Given that the ballast is magnetic, you can find out easily enough if you are willing to take the ballast apart. Each 400 watt lamp should have it's own ballast core. Attached to each core should be either one or two components. One is a capacitor. The other, if present, is an ignitor. If there is an ignitor present, it's a pulse start. If not, it's a probe start.