Even though Account B won't own any land from October 23 to November 2, that account will still have to pay the entire 30 days worth of tier. Account A will also be paying for the additional 2.5K group donation starting October 23. Even if Account A nd B only had land for 5 minutes, it will still count for an entire 30 day billing period.
So yes, for about a week, you'll be paying for land twice.