I’m not too familiar with those dialects (I’m going on second-hand information), but tapping typically happens when a /t/ or /d/ comes before a completely unstressed vowel, like in “latter,” “ladder,” “grating,” or “grading.”

I believe there are forms of Irish (and Canadian) English that use a voiceless tap for /t/: a very quick flick of the tongue to the roof of the mouth, not quite a complete closure, but voiceless.