I contest that the order of this list is alphabetical (if it were, an easy though ugly workaround would exist). I bet the order is tied to Android's account list, and there, the google calendars are on top. Google doesn't allow deleting all its calendars, so it's always google first, it seems. BC2 does allow hiding google's calendar(s) elsewhere: we can filter and order calendars for the colour buttons by marking them favorite or not (where the last one marked favorite becomes last in the list). The import dialog could use that ordered selection instead of whatever list it invents now.

I regularly book gym classes that are released one week ahead of time through an app, which creates a new event with the same title every time. Business Calendar assigns the event to the last used calendar, but I would like an option to assign it to the calendar last used for an event with the same title instead.