Yes, it's simple. If you're registered as resident in an EU country by the end of the year, then you can continue to live and work there (that specific country). If you're not, you can't.
If you mean freelancing or a secondment or detachment to an EU base, I think it would be ok, limited to 90 days? On the other hand, American FedEx and ups crews seem to get much longer. Not sure how that works.