Thanks, Iceweasel.

Those two sources certainly confirm that effective from 01/01/2012, Serbia
is supposed to recognize insurance coverage for vehicles with registration/ plates from 33 European countries, including the UK, without the driver presenting a separate Green Card document, when crossing into Serbia.

BUT, as noted in earlier posts, there's still some ambiguity.
The UK FCO website:
Serbia travel advice
says, specifically (with respect to UK registered vehicles)
"European green card vehicle insurance is now valid in Serbia. However, the requirement to hold a green card is no longer in effect from 1 January 2012. You are advised to confirm that your insurance company recognises that your policy covers Serbia.

That would suggest that the UK FCO recognizes that not all UK vehicle insurance policies for UK registered vehicles necessarily cover Serbia; that may still depend on the specific UK insurance underwriter.

Similarly, it's still ambiguous/ uncertain that non-Euro registered vehicles, e.g. from the US, Canada, OZ, etc, with temporary Euro Green Card policies issued by European companies, are covered under this "new" Serbia agreement; that may also still depend on the specific EU underwriter. As of 2011, those temporary EU Green Card policies from ADAC/ Arisa, MotoTouring/ Italian UTI, etc, did not cover Serbia, and those vehicles still had to buy separate Serbia border coverage at an additional minimum monthly cost of
about 60 Euros.

This appears to be a "transition" year; it remains to be seen whether all UK underwriters will recognize the Serbia change, and whether all EU companies writing temporary Green Card policies will also include Serbia going forward in 2012.:confused1: