Points to consider

• JRC personnel is not entitled to diplomatic plated cars but is entitled to official diplomatic discounts in their price (direct from the car company and not the particular dealer)
• The percentage discount depends on the particular car company and the policy of each company is variable itself (so a diplomatic discount available today may get better or worse as time passes in an unpredictable manner)
• Currently discounts I came across range from 10% to 30%. (Mercedes is about 10%, VW is 15%) Historically Saab and Volvo have been providing the largest discounts.
• For example, currently a brand new (standard equipment) 320i Cabrio costs (44,200 EUR - IVA 20% inclusa, IPT immatricolazione esclusa) in Italy but BMW headquarters quoted the following diplomatic price to me for the exact same car: (27.630,00 + 19%IVA = 32879 Euros) or about 26% discount (Italian price from bmw.it site)
• You will have to pay VAT (IVA) only once and the VAT percentage will be that of the country of destination of the car. BMW for instance gets a guarantee deposit cheque of the 19% VAT that is not cashed. They hold on to the cheque until they receive proof that the VAT has been paid at the country of destination.
• Car companies that are doing this (e.g. BMW, SAAB, Volvo) usually have links to their Diplomatic Car Sales department on their international web sites.
• You can have the car delivered to your dealer of choice (throughout Europe) or pick it up with export plates direct from the factory or the closest port.
• Furthermore, diplomat or not, it is currently a smart move to buy left-hand side drive cars (e.g. BMWs) from the UK as you would profit from the presently convenient exchange rates of the GBP. For instance the same 320i Cabrio costs 27,182 GBP net and bringing it to most EU countries you would have to pay a 19% VAT (in the UK car VAT is only 15%) which means a final price of 32,346 GBP or, based on xe.com rates, 35,177 EUR which is still much cheaper than price of that car in a country like Italy. Obviously the actual price you will be paying will depend significantly on the exchange rates used by the banks involved in the money transfer. Not all UK based BMW dealers work with left-hand side drive orders but some do and you can find those by contacting them through the bmw.co.uk site. One that I know of is:
  

  Charlie Menard, 
  BMW Park Lane International Sales
  Tourist and Export Specialist
  Email: Charlie.Menard@BMWParkLane.co.uk 
  Direct Tel: +44 (0) 207 495 9522
  Internal Extension: 4522 
  Fax: +44 (0) 207 318 9317 
  www.bmwparklane.com 
  www.miniparklane.com
  

• There may be other such opportunities in other EU countries that do not use the Euro as their currency
• There is a chance that diplomatic car purchases from the UK in GBP actually cost less than diplomatic car purchases in Euros. To cover this possibility I have asked for a quotation and still waiting on it; however, I think the chances of this possibility being true are small. Still, there may be other disounts they can give you that do not even require you to be a diplomat.
• In the case of Greece there is an illegal (as far as EU laws are concerned) tax imposed on newly bought and imported cars. Cars with engines of 1,800cc to 2,000 cc have to pay a whopping 40% on top (and 1,600 to 1,800 a 30%, 1400-1600 a 20%, 900-1400 a 12% and even tiny cars under 900cc, of the latest green technology, a 5% - why?). This is 40% of the net price shown on the car’s purchase receipt.
  • Cars with diplomatic plates are exempt from this tax (but a JRC official’s car would not have diplomatic plates on their cars)
  • There are two ways I know of to avoid, at least partly, this blatant piracy
    • Do not import your car directly to Greece but first to a country like Italy (if you are currently staying in Italy for instance). After 1 or more years you will pay much less to import the car in Greece as you will be importing it as used (and the price used in the calculation will be that of a used car). Specifics here: http://www.gsis.gr/teloneia/xrisimes_plirofories_teloneia/efk/efk5.htm
    • Besides another country’s plates (in case you do not want to register your car in another country for whatever reason) you are able to buy the new car with export plates lasting up to 1 year (the car company also provides a special car insurance plan for this kind of plates for their duration). This 1 year should actually get your car to be considered a used car when you eventually take it through the import process but as this is an undocumented and subtle process (and people I called in the Greek customs did not know much about) it would be better to get someone to guarantee its outcome before you engage in it.
• Diesel cars are not allowed in Greece in the areas of Athens and Thessaloniki