It's not really on the technical side of thigns, but the unification of IC cards across transportation companies has a good write up [0] that has a bunch of fun details. My favorite thing is how the people working on the project just had a bunch of card readers from various transport companies all in one room.
[0] https://www.ejrcf.or.jp/jrtr/jrtr62/pdf/6-15_web.pdf