I don't think it as simple as EASA accepting the Chicago convention which they tend to ignore as EASA is not a contracting state. They make the individual countries do the dirty work.
The CAA website has a FAQ section;
http://www.caa.co.uk/docs/2330/h-FAQs%20May%202012.pdf
Item 26 which states;
"Under EU regulations a validation will be required for such a pilot to fly an aircraft registered outside the EU if the operator of the aircraft is based in the EU. For Example, if the Operator of an N-Registered aircraft is based in the UK, the holder of an FAA licence will have to hold a validation issued under EU regulations by the CAA to fly an N-registered aircraft in Europe"
I have not kept track of the latest developments (if any) as it does not affect me directly. The NBAA website is only focussed on N reg aircraft visiting the EU it does not answer the case of a EU based company with N reg aircraft.
Mike Echo