I think you are absolutely correct.
One of the problems with the research is that in Australia, random breath testing was brought in along with lowering the BAC to 0.5, with high publicity, and enforcement, etc. The state of Victoria has something like eight “booze buses”. They're out on the road every day, and they do somewhere in the neighbourhood of three million breath tests in a state that has a population of about six million. Just about every driver is being tested, so, yes, there's no question that no matter what you put in the law, if you don't have enforcement, then it's not going to work.
The Irish experience is interesting, because they brought in 0.5 first, and then they brought in their former random breath testing. You could divide those two. Random breath testing is one of the measures, but it's a relatively small country. I have the numbers here. They do about 70,000 road checkpoints a year. That's a couple of hundred every day.