Pro rata deduction of input VAT only after 1 January 2016

On 1 January 2016 in Poland, new provisions on pro rata VAT deduction entered into force.
For some time, both tax authorities and some administrative courts claimed that taxpayers who pursued business and other activities and purchased things that were used at the same time in both these kinds of activity already had the duty to adequately separate input tax concerning non-economic activity at a formula they determined themselves.
But neither case law of the Court of Justice of the EU nor the fundamental principles of applying the law justify this standpoint.