Like you, I would be pleased to have a bees nest! I haven’t actually had one in a hog box, but more than once in the enclosed bit above my front porch, and a couple of times in the ground and a couple of times wasps in bird boxes. Also I filled a box a couple of years ago with bits of wood, corrugated cardboard etc. and in no time at all some bumble bees had moved in. So I’m not at all surprised that they would find a hog box a good place.
Also in his book ‘Hedgehogs’ Pat Morris says of ‘wild’ winter nests “… This type of nest will last well over a year, but those built one winter are never used the next winter, even when they are still available. However, other things such as bees, wasps and wood mice eagerly take them over. …”
You didn’t mention what type of bees, i.e. bumble or other? Mine were all bumble bees. I’d be interested to hear how they get on.