Complex sentence: In 1995, the H-series were succeeded by the T-series, which replaced earlier H-series subsets, until the remaining H5 and H6 subsets were completely replaced in 2014 by the current latest model, the Toronto Rocket.
Split into simpler sentences: In 1995, the H-series were succeeded by the T-series, which had replaced earlier H-series subsets. The remaining H5 and H6 subsets were replaced in 2014 by the newest model, the Toronto Rocket.