The passport control at Malmo/Hyllie has been non-existent for days now and that’s not going to be why a major new infrastructure project of this sort will or won’t happen. Of my last seven crossings (spread over three weeks) from CPH to Sweden by rail transport, I’ve not had to show any ID/passport.
I would settle for them just making the existing rail lines more reliable between Malmo and Hassleholm and between Stockholm and Jonkoping and Stockholm and Vasteras/Eskilstuna.