This - found via nostr:nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpqzadn9vrh0g57r498a70u2k7ducc7030xpvlyl64nnrx2stc3pc3qpwpput - has a little detail on extending trains from Slovakia and Austria/Hungary to Chop 🇺🇦 the 20km further to Uzhorod https://unn.ua/en/news/ukrzaliznytsia-opened-ticket-sales-for-direct-trains-to-the-eu-on-the-european-gauge-list-of-routes

They will extend EC 146 (that is diesel hauled on the border section anyway) https://www.vagonweb.cz/razeni/vlak.php?zeme=%D0%A3%D0%97&kategorie=%D0%A3%D0%97:%D0%A8&cislo=%D0%A3%D0%97:146%D0%94:%7CM%C3%81V:146:Tisza%7C%C3%96BB:146:Tisza&rok=2025

Extending R 961 is more interesting as that's electric https://www.vagonweb.cz/razeni/vlak.php?zeme=%D0%A3%D0%97&kategorie=%D0%A8&cislo=961&nazev=&rok=2025