said by Mr Matt:that is an issue that is addressed in Alkizmo's Federal Pioneer switch, has a neutral breaker tied to the hots. the square D ones that i have seen dont switch the neutrals
You will also want to make sure that the generator you purchase is compatible with an interlock. Some generators have GFI's that protect the 240 Volt Outlet and tend to trip out unless you have an isolated neutral which an interlock does not provide. Occasionally there is a post in this forum requesting information on how to resolve those GFI issues.