[nkmnz]

In fact, you can run any form of European legal entity from any country. I.e., I can create an spółka z ograniczoną odpowiedzialnością (sp. z o.o.) in Poland, but run the business in Germany. It would be complicated and stupid, but legal.

[badpun]

You can't hire people cross-border though. That sp. z o.o. would need a German subsidiary if it wanted to employ people in Germany.

[nkmnz]

You can! A foreign EU company just needs to get a "Betriebsnummer" (company number) from "Bundesagentur für Arbeit", which doesn't even require a Betriebsstätte (permanent business establishment, a branch that is not legally independent) or a "Zweigniederlassung" (branch office, legally semi-independent, but still part of the same entity) - and certainly not a subsidiary that has it's own legal persona.