Yeah - I think this is my mistake from that post. The Form P talks about Aberdare services running via the City line explicitly; it doesn't actually discuss what happens to them when they get to Central because that's out of scope for a document that's purely about the Core Valley lines. Since it didn't mention linking Aberdare services to Merthyr services, I assumed that the Aberdare trains would reverse at Central and go back the way they came. However, the idea of running those services as a loop has been proposed for a long while, so now that it's been announced, on re-reading that the consultation documents it's clear that they didn't rule out that option, but didn't say it would happen either. Oh well.