I have no scientific data, but as a British scientist who has worked in France, Germany, The Netherlands and Italy — and has heard Continental European politicians using English, I would say that the accent/pronunciation is usually British†.
Part of the reason for this is, I would suggest, that it is customary for university language students to spend a year (generally teaching) in a country where their language of specialization is spoken. Britain is obviously a closer and cheaper venue than the US, and there are exchange schemes between European countries. When these students become schoolteachers, they teach with the accent they have acquired. They probably also use British terminology and spelling, although school textbooks may negate the latter.
(Similar reasons explain the use of Castilian Spanish — rather than S. American Spanish — in Britain and Continental Europe.)
† Obviously most non-native speakers have an accent influenced by their native language, but one can still tell the difference between British and American styles of pronunciation.