I'd expect it is their intention to add them, but they are most likely going to prioritise DLCs that have been updated recently.
The only thing we know is they fully intend on bringing the preserved routes to Epic but there is no timeframe. Keep an eye on the roadmap
They have no reason to port them. If you take the Preserved collection route(s) and loco(s) from the steam version and put them in the 'Paks' folder of the epic one it works fine. All they have to do is get the achivements and get it approved
