UPDATE: Live streaming from the Swimming Championships is available here on ejc2013poznan.eu. They are streaming both from preliminaries and the finals
The live webcast will be available during the entire championships from July 10th to 14th with morning sessions at 09:00 and afternoon sessions at 17:00 according to the competition schedule.
The Poznan 2013 European Junior Championships organizers are streaming LIVE in good quality from the Diving Championships, July 3rd to 7th, apparently even from the prelims. This bodes well for the Swimming Championships also ;-) See ejc2013poznan.eu, Start lists and live results here.