This is technically not possible and it is not BC's fault. It's actually how Android works. All of your apps use the same sync functions of your device. Android - once synced the calendars - stores them in the calendar storage on that particular device. This is where the apps pull the calendar data from. This is also where your local calendars are stored. Since all of your calendar apps access the same storage (based on the calendar storage permission you grant in Android settings), they show the same data and it is not possible to divide the display. For that particular reason why introduced the Favorite Bar function in BC, which allows you to quickly toggle calendars.