The bees in this case were a small colony that spawned Spring swarming due to a limited amount for space for comb. Each and every cavity of a beehive has its own challenges and characteristics. In the wild honeybees normally seek out a dry space of a gallon or more in size where they can regulate the temperature and stay dry. In this case, a building more than 60 years old has seen some wear that resulted in the top plate lumber deteriorating from water damage. The foundation of the wall has suffered some undermining caused by tree root growth at the corner of the building and brought minor cracking to the cinderblock corner as well allowing mortar to crack. A honeybee only needs an opening of about 1/4 inch to find access.
The photos below give you an idea look at how to access bees in block without compromising structural integrity. Saw cuts were only made in mortar joints except where division of the block was required to maintain integrity to the support. Read the photo descriptions.