There are three issues i believe with plain packaging from the manufacturers point of view.
1.of course they are scared shitless that it will impact sales, and probably will
2. I do believe they genuinely have an issue with someone else having a veto or control over their branding and whats called their proprietary branding.unfortunately for them it doesnt appear to be safe under irish law
And the third, the most contentious one is that it will show that the manufacturers are complicit in the illegal distribution of cigs into states as if plain wraps are found being smuggled, and testing proves that they were manuf. In a legit factory then the manufacturer will have been complicit in the distribution