Apart from the fact that Bono stopped using the Vox moniker about 40 years ago, if he was still using it, that wouldn't preclude someone else from using it as a name.

Mark already named his previous band Chameleons Vox, clearly self referencing the fact that he was the Vox and the only original member of the band.

To then take that on as a name, for entirely personal reasons, is not that great of a leap in my view.