Back in 2018 I was walking to my out-apiary when I heard loud buzzing above, and saw a swarm entering this tree. Since then I check them every time I check my hives and then they have thrived (I am writing this 2 years later). I've never seen them bothered by wasps or other predators and they overwinter without a problem.
They're a bit high up to examine closely, I use binoculars; I once hauled a 5 metre collapsible ladder over and climbed up, to find the entrance was still 3 metres above my head. Even if I wanted to "manage" them I don't think they're accessible.
Genetically, they are going to be "local" bees as I have allowed my hives to open mate with the plentiful wild bees of the area for many years.
The cavity must be relatively thin walled for a hollow tree but obviously provides adequate insulation. It's obviously a vertical cavity, like a chimney.
23 May 2018
Total reported by Paul is 1