I see the policy is GB-wide, as rail industrial relations are a reserved matter, though consultations are promised with the devolved administrations.
I'd expect the Welsh Government to take a different view of its MSL services within Wales, given the acres of white space on the map, extending well into England.
The map is heavily skewed to the lines with centralised signalling (ROCs, SSCs etc), and against routes with local manual boxes (such as most of Wales/Borders).
The WG might take the view that some limited services should be provided, eg on the Cambrian (ETCS) or routes around Chester* (with a PSB).
That's if the Labour-Plaid WG can bear to annoy the TfW unions by requiring some internal services to operate.
Scotland does seem to have got a decent central corridor service, but the lack of Edinburgh-WCML links is surprising.
* I see Merseyrail has a full coverage, so that means Chester PSB will have to open for them.