The availability of good models alone will create a market, marketing in some form to bring it to the knowledge/interest of that potential larger market is what will really sell the product. Let's face it, you can't buy something that's not available and very few will look for kit etc just to 'get into' the Irish outline. Parents or grandparents not going to go around scratchbuilding for months before one's birthday.
After all, many of us as children bought British outline because that was what was available for you or you parents to buy as gifts etc. Those childhood experiences combined with the greater variety/different rolling stock available to the maturing young modeller in British outline is probably what prompts that interest in some of the modelers on here including some of the IRM themselves.
I have no real interest in British outline (anymore) but it doesn't mean I don't have the occasion APT or Canadian loco hanging about among my Baby GMs. I'm sure a few on here have an ICE or some Marklin/Roco stuff.
I think you make a good point about the expectation from a European market when coaches with lighting, opening doors and real biscuits for the passengers is maybe not the standard but certainly available (maybe not the biscuits). You'd have to say that the IRM products are certainly good enough to compete, so who knows.