For anyone who knows railways will know that Ireland has a rather different rail gauge to the rest of the continent of being 5ft 3in, a gauge that can also be found in Australia and Brazil.

However Ireland's first railway, Dublin and Kingstown, was built as standard gauge but it found itself in conflict with another gauge of 6ft 2in and this led to in the end to be a comprise of the current gauge we know today.

However I've always wondered what if Ireland had adopted standard gauge from the start of how different things might have been? More rail boat crossings between Britain and Ireland (Irish Mail Train) or perhaps during British Rail's disposal of steam they end up cascading most of them across the Irish sea for use? Maybe it makes the idea of a rail tunnel between the two nations more possible?

I suppose really it's one of those hindsight moments that things could have worked out better for all? Any suggestions on the matter?
Given the wide range of companies that ran Irish rail lines I'm not sure how coordinated you could get them, integration was never a strong suit. TBH I don't see a different rail gauge having the effect on routes between Ireland and GB, to me that would be more connected to economics rather than transport, the Irish economy would need to be better to justify more trade. Then you get into the questions about how Ireland followed the UK in running down the rail network, along with the running down in NI as well.
I'd think it is overshadowed heavily by the deep issues of Irish nationalism. After all Britain itself had a long period of wildcat RR competition and settling to a "standard" gauge there took considerable time I believe. Certainly in the 20th century, a common gauge might be relevant to trans-sea tunnels or bridges...but by the time this is something that could be technically possible let alone economically justified, the Irish Revolution would have come and gone, and Ireland a separate Republic desiring to maintain an arm's length relationship with the UK. Of course geographically speaking Northern Ireland, which presumably the UK hangs on to for demographic reasons, is the very part of Ireland most suited to be linked to Britain. So if in fact the same gauge had prevailed, which you see I assume has subtle at best effects on overall Irish development and economics and demographics, the UK might more plausibly toy with the idea of a rail connection to the NI stump of former British rule.

Of course by mere butterflies or by a systematic argument, Irish independence might not be an inevitable thing. Maintaining dominion over Ireland seems more likely to happen by dark and violent means, involving a much more repressive UK developing. Getting continued union by consent of the Irish people...that takes some fancy dancing and probably POD pretty early. Early enough in fact to coincide with the shaking down of Irish rail lines to use the same gauge as in Britain in fact...but I can't see the choice of gauge having any particular bearing on either having a more conciliatory relationship between British government and the Irish, or on enabling a British regime that simply demands and can expend the force and terror to get submission.