There is a longer article https://www.ejrcf.or.jp/jrtr/jrtr15/pdf/f38_tec.pdf from a series on Railway Technology from the Japan Rail and Technology Review https://www.ejrcf.or.jp/jrtr/technology/index_technology.htm... . It contrasts ballasted track with slab track and purports a 9 year breakeven on the higher construction cost but reduced maintenance cost. It notes that the main Shinkansen from Tokyo to Osaka is ballasted track and I understand it still is. Mind you how you could ever changeover on this super busy line is going to be somewhat difficult.
