BJCC
Whatever they have been prosecuted for, it could not (scientifically) have been blood alcohol levels based on a urine test. No laboratory would make the claim that a urine test reflects blood alcohol. Labs just carry out tests on demand.
Making a urine test the basis of a prosecution is very problematic.
There are lots of papers in the literature (since this is a well understood subject). For example:
http://www.aic.gov.au/publications/other/dic1992/14.pdf
(just to turn your world upside down again)