The answer to both your points may be: by issuing their own NI 43-101.

I don't know about any representations about gold "reserves" at Las Cristinas by GRZ. As far as I know they have only shown resources. I know Crystallex showed nearly 17m ozs of reserves (proven and probable).

It does surprise me they called the Crystallex data unreliable. I don't know why that would be. One would expect it to be cheaper to use the Crystallex data rather than conduct their own drilling to turn resource into reserve but apparently that is what they are going to do. Maybe Crystallex refused to sell the data, maybe they refused to buy it (at the price Crystallex wanted), maybe the combined mine needed new drill data anyway, maybe they have to include copper as well as gold, maybe the data really is unreliable.