as DonT mentioned it WOULD not be necessary ,if more car manufacturers fitted these devices

No, DonT said that what is needed is to fit ALL cars with the Breath Alcohol Immobiliser. Even if such a thing could be done, it would take years to do, plus the years of legal entanglements which would result from the fact that people wouldn't want the devices on their cars. I'm not convinced that the devices couldn't be tampered with, anyway (what can be programmed can be deprogrammed or reprogrammed, and what can be attached can be removed or at least disarmed).

Meanwhile, Ireland wants to address its drinking-and-driving problems NOW. Seems like lowering the limit is the best short-term solution... and, perhaps, an ideal long-term solution as well, because it will persuade many people to change their habit of drinking and driving. In my opinion, this is better than fitting all cars with a device that forces compliance, which would only increase resentment rather than induce social responsibility. I think the ultimate aim should be to change the mindset of society toward more responsible behavior, and I don't think that those immobilizing devices achieve that goal.