Hi Alan, it’s doable for sure. You can open it up with a chain saw, then find the brood mass before placing it into a box. I have some empty boxes if you want to borrow for a while until you make one. I did one with a bloke last year. There was 2 colonies. We got one each plus I cut the old dead tree up for fire wood.
Sometimes you can split a tree colony, they get that big.
Thanks Jeff. It’s in the Mountain Creek reserve so I’d reckon I’d have to get permission (and a chainsaw) from the Council before venturing in there. It looks like a large one from the outside and I’m assuming the tree to be hollow as well. I’m thinking I’d like a hive. I know there’s heaps that forage around my trees. I’ll keep you posted.
I bet that the council would be duty bound to let you rescue native bees - it is the right thing to do, after all. Knowing the kind of guy he is, @JeffH may even be willing to come and help you with a chainsaw too if he has one. He is just like that, and he has an existing interest in native bees! 
I hope you do go and rescue them. They won’t enjoy the rain if their home has been compromised. 
Yeah, let me know how you with them Alan. I have a chain saw. cheers
Thanks Jeff. Very kind of you. I’ll call the council up tomorrow and let you know the outcome.