Since Lithuania is an EU member, the EU could hardly refuse. As for the Germans, they’d probably wring their hands and complain bitterly but allow it. The Moscow paid for SPD would probably prefer a “negotiated” settlement with Poland and the Baltics making all the concessions, but the mainstream are close to fed up with Putin’s and Lukashenko’s antics already. The Bundeswehr would be hard pressed to contribute anything besides a token force.
What ‘Lukashenko antics’? I see Poland and Lithuania actively meddling in Belarusian affairs for a couple years already. I don’t see Lukashenko doing something in these countries.