Regulations for shower over bath

Hello,
I am going to check with the VBA on Monday but I thought someone here might have the answer.

I read somewhere that it is a requirement of Building Authorities and Australian Standards that acrylic baths that have a shower over need to be "fully supported with a mortar mix". I cannot find verification of this online.

My contractor has drilled down the old mortar bed to fit the new bath in and he has filled with foam. I want to make sure that it complies with the regularions.

Thanks