You can certainly get an estimate but the exact impact depends upon information that doesn't exist yet and metrics will easily be misread even without any active deception or conscious metric gaming. Say consumers either treating cheap reusables as disposables or reusing nominal disposables woule throw it out of wack and even accurate accounting could have perverse impacts.

Not to mention that there is also a difference in environmental impact of the same resource consumption that differs by location - brewing using great lakes water vs a depleting aquifer. Or power usage in aluminum from solar or geothermal vs burning coal to do it.