@Piboso: just realized that in the "classical" output plugin interface (i.e. not the new RaceData stuff) there's a pitfall.
In SPluginsKartSession_t the filed m_iSession has this comment (for KRP):
/* testing: always 0. Race: 1 = practice; 2 = qualify; 3 = pre-final; 4 = final. Challenge: 0 = waiting; 1 = practice; 2 = race */
But there's no way to know in which event type one is (testing, race, challenge).
Notice that for GPB, MXB and WRS the problem is not there (as the interpretation of the fields does not depend on the event type).
The new racedata stuff handles the thing properly, that's why I noticed :)