EASA has released its proposals on maintenance of foreign reg planes based (meaning: long term parking) in the EU.
The relevant bit for small aircraft seems to be on page 9 of the
PDF
The bit relevant to SE or ME pistons appears to be the very bottom row - if I understand it right.
ISTM that it hangs on the meaning of
>ICAO Annex I licence, or
>o Qualified maintenance
>organisation, or
>o ICAO Annex 6 maintenance
>organisation
It appears that "ICAO Annex I licence" means an A&P (or maybe an A&P/IA) and "Annex 6 maintenance organisation" means an FAA Repair Station.
The provisions aimed at jets etc seem "interesting" to say the least.
Not sure who is going to define the line between a visit and long term parking.