Fortunately, the hives are on the sacristy roof, which is considerably lower than the cathedral, it is way bellow the level of the windows, which all survived, and the sacristy is sticking out away from the main body of the cathedral.  And the stone walls around the roof area and the  would give more protection against the heat.   The fire destroyed the wooden roof structure, and in 3 places the vaulted ceiling collapsed, but once the burning wood fell down the firemen were dousing it with water.  That is why so much inside is also OK. 
buttresses
This picture shows bit more how far the bees were from the cathedral and how much higher the roof is



You can see where the fire made most of the damage - all the yellow