A light touch, such as when one's arm gently presses on a female's, can be deeply sensual. I remember at uni there was a girl I liked who had a boyfriend but there was a connection between us. She asked me a question about the computer and I got up and stood behind her in class and started to move her mouse. As I did, our arms gently brushed against each other's and I held it there while fixing the computer, but my mind had been taken over by a somewhat sexual passionate sensation of warmth, but even though our arms were lightly touching and we could each have pulled away, I didn't want to, and I suspect she didn't want to either as she didn't pull away, even though she did have a boyfriend.
I've long noted this sensual sensation of a light touch, and it does happen occasionally. I don't believe all women sense it, but some do. As to your question regarding girls on the bus in your case then yes, I would agree that those who didn't pull away are taking some pleasure from it and may like you, or at least your touch, or they may not have noticed. Those who pull away may be dating, or they may not want to feel this sensation or just want some space as I'm sure Ireland is culturally similar to England in that people don't touch and so any touching would make them feel uncomfortable.
A few years ago a woman older than me had her arm touching mine in an innocent way, but because I didn't like her I pulled away, quite abruptly in fact. She noted this and was hurt by me doing so though didn't say anything at the time, but she did mention it the next time I saw her, a week later and was rather upset that I had done so.
Ex girlfriends have mentioned this, and they did like a gentle touch on their body, and some a gentle stroke through the hair, and they commented that they like this light touch and when I stopped they often asked me to continue. But the impact is felt even more with a woman who you're not dating, especially if there's some invisible chemistry between you which can only be felt through the mind, but can be released and exchanged through touch. Generally speaking, the girls who pull away have a boyfriend and so naturally don't feel comfortable, as even the lightest touch can arouse the senses. In fact, the lighter the touch, the stronger the arousal.
A James Bond theme, I think Goldfinger or The Spy who Loved Me says "he's got the lightest touch". I think it's by Carly Simons but I'd need to check.