The document at the link supplied by the Flying Lawyer simplifies the situation somewhat. If I have read it correctly, it indicates that for screening stage, the standard breath test will be applied using the current equipment that has met the more stringent aviation requirements.
If this test is positive, then arrest will follow and blood and/or urine samples will be taken for laboratory testing.
But subsequent attendance at court will probably only take place if there is a positive result from the blood or urine testing.
So it would seem for practical application of the new law, one might take a reasonable guess at the required recovery time after consuming alcohol based on personal experience. But, before reporting for duty, one should take a breath test using the same type of equipment as used by the Police.
As Blacksword points out, relevant drugs, levels and testing still remains a mystery to all.