I don't know what the situation is with Canadians who flew in the RAF but the next of kin of a British RAF personnel can get info about their career:
http://www.gov.uk/guidance/request-r...vice-personnel
With this you could get a squadron number and with that there may be a squadron historian, association or records at The National Archive that would answer more.
A plane being shot down by a U-boat post war would surely have been written about somewhere - newspapers, U-boat war histories. It is also possible a War Diary (Kriegstagbuch) exists for this submarine. The US National Archives used to have such diaries on microfilm. There also exist U-boat archives - Google 'U-boat archives' and some places turn up.
I would think the U-boat captain would have had some explaining to do so again there would have been interviews with him and his crew.