I know for a fact that my CALI client cannot withhold taxes for me because the work is performed overseas despite fact that I am a US citizen.
Because you are not an employee - but a self-employed contractor - and has a valid SSN - and are US citizen - your client is not required to withhold income tax, but they may do that for your convenience - if they do that for you - the withholding amount would be reported in the box 4 - http://www.irs.gov/pub/irs-pdf/f1099msc.pdf
How then can it require me as a foreign employer to withhold US taxes for my employees who are not even US citizens? NOw, as far as FICA and such, there is not even a requirement that I contribute to such a system upon proof that I am covered and paying into a Greek pension system (which I am). Same as my Greek employees and contractors. So, as far as withholding of FICA for folks working overseas, for me (a foreign employer) not sure what you are suggesting makes sense.
If your business is registered and located in Greek - and all services are performed in Greek - all payments are e made in Greek - etc - so your business activities are under the Greek jurisdiction - all payments and reporting should be according to the local - not US tax law.
But in this case all payments to your employees or contractors are provided by the Greek legal entity in Greek - and not by your personally from the US.
If that assumptions are correct - you are correct - there would not be any IRS or FTB reporting requirements.
However - if payment is made by the US person or by the US legal entity - we are back to what I wrote above.
We also need to check it the tax treaty between the US and Greek have any regulations this matter - but there still will be reporting requirements.
The main publication which covers tax issues for Aliens is 519 - http://www.irs.gov/pub/irs-pdf/p519.pdf
Let me know if that helps