Yes. ThermaNiches are fabricated from the same board as ThermaSheet which is waterproof.  The joins are also waterproofed at the time of manufacture.

However, as they are installed into brick wall and gyprock walls, there will be gaps between the wall and thermaNiche which will generally get waterproofed as part of the waterproofing of your bathroom, especially when the niche is being installed in a shower or above a bath.  As you are waterproofing part of the niche, we recommend waterproofing everywhere inside the niche at the same time.