Huawei Access Terminal Box ATB211 installation

My daughter has just moved into a flat which has the ONT installed inside an ATB enclosure. I‘ve stolen a photo from another poster of The box in question

I want to remove the box/enclosure as it’s getting in the way of some cabinetry. I had assumed it would be a simple case of unplugging the ont; unclipping the ONT from the box and removing the box from the wall.
However, I can’t figure out how the ONT attaches to the enclosure. Does anyone have an install guide or an idea of how these enclosures are installed?

thanks.