It's a bit of an unfortunate fact that this was published in this book rather than in a peer-reviewed paper. I believe I have somewhere a scan of at least a phylogenetic tree in this book chapter, but don't know straight away where I put it...
The tree in this paper =>
http://molevol.cmima.csic.es/carranza/p ... nyNewt.pdfshows that this was a rightful split, since the old parts of Triturus s.l. were less closely related to each other than to the Pyrenean brook newt on the one hand and the Tyrrhenian ones on the other. As such, the old Triturus s.l. was polyphyletic. Alternatively, you could include all (and apparently also Neurergus) into a single supersize genus. Given the heterogeneity among these taxa, that seems not really desirable.