CASR was a multi stage project the work they did do enabled the 4tph service at the Cardiff end. The later stages would have made the changes further up the valleys. This has of course been superseded by the Core Valleys Line scheme.
The Cardiff Area Signalling Renewal (CASR) project improved station entrances, added new platforms, and upgraded track and signalling to increase…
www.railway-technology.com
So what infrastructure, in addition what is detailed in this article, did CASR involve? It's worth noting that even with the additional platforms further up the Valleys at Pontyridd and on the Rhymney line that CASR did involve, TfW will still be adding in more passing loops and new platforms to enable 4tph from each Valleys terminus to be possible.
As I said up thread, and as is stated in the article, CASR allowed
up to 16tph through Queen St, but operating with heavy rail DMUs, that wouldn't have allowed for
any slack in the timetable. Even the slightest service disruption would've led to timetable meltdown. Plus if you have say 4tph from each Valleys terminus with CASR, what about the Coryton line? And that doesn't allow for any additional terminators at Pontyridd and Caerphilly, as is planned by TfW.
It's also worth noting that from start to finish, CASR took 4 and a half years! As with all NR infrastructure schemes it was over budget and heavily delayed. I remember commuting through Cardiff in 2014/15 when the work on the new platforms at Central and Queen St had been started but was abandoned for months and nothing was happening.
And of course CASR didn't include electrification, and anyone who thinks the Valleys electrification scheme would have gone ahead if left up to DfT and UK Govt, when they were cancelling every other electrification scheme across England and of course cancelled Cardiff to Swansea, really is living in the clouds.