Is this due to major engineering work closing down the lines?
Well, neither CP nor Renfe mention any reconstruction works or cancellations. Also short cursory search (both in Spanish and Portuguese) doesn't show any notices about problems with "Sud Expresso" or "Lusitania" (also missing after Feb 2), so it does look more like timetable change or something like that (especially since even some domestic Spanish trains in that region doesn't show up on Renfe website after the date)
And even if it is about line reconstruction, it's much more likely that there will be some bus substitution for certain leg of the journey, don't think all those train routes will be left without connection
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