If I have two business objects on the same form and neither of them is the primary business object, and I have two MaintenanceFormToolStrips on the same form... can I bind one toolstrip to one BO and the other toolstrip to the other BO?

No, the MaintenanceFormToolstrip is designed to call the methods on the parent form.  And the parent form, in turn, uses the IncludeInForm settings to call the corresponding methods on the included busines objects.  There's no way to have one MFTS use one business object and another MFTS use another business object unless you create your own toolstrip.