I'd be very interested to know where you've read that. My impression from
the thread on the project is that very little has happened in the last 15 months (though posts that are strictly on-topic are outnumbered in the thread by broader discussions). Works over Christmas 2022 were cancelled and a works compound was reportedly closed down.
There's been a big slowdown in the Scottish electrification/decarbonisation programme generally, for financial reasons. The Barrhead project was not affected and has been completed, and the East Kilbride line has now been properly started, for completion by the end of 2025, but everything else seems to be slowed down, including the proposed partial electrification of lines in Fife and the Borders line. An updated version, or "refresh", of the 2020 decarbonisation strategy document, originally promised for spring 2023, is now said to be due out soon.
Partial electrification with battery trains (BEMUs) is certainly the policy for Fife, but even if Haymarket to Dalmeny were completed, I don't think the few (9 or so?) miles beteen Waverley and Dalmeny would be enough to allow them to be introduced until further wiring is in place in Fife itself, and until the "refresh" document is published we don't know when that will be.
The rebuilt Levenmouth branch, due to reopen in June, has been equipped with foundations for electrification masts, but no actual masts. The Thornton feeder station, which will eventually supply the lines to be electrified in Fife, has not started construction, and is now supposed to be ready by September 2026.
The most recent published policy on rolling stock acquisition dated from summer 2022 - see the beginning of the thread linked here:
An advert for a tender for legal services for the above (https://www.publiccontractsscotland.gov.uk/search/show/search_view.aspx?ID=AUG455691) gives some more detail on the fleet plan ScotRail Trains (SRT) plans to replace 65% of its train fleet (around 675 carriages) in the period 2027 to...
www.railforums.co.uk
but this was before the big slowdown. Probably the upcoming decarbonisation strategy refresh will include or be accompanied by an update on rolling stock procurement.