I just unlocked the Alliance Infiltration Unit, which has the (imo so far) amazing ability Snap Freeze. I checked if I could source or detonate any power combos, and it turned out I could detonate Tech and Fire combos, and source the Cryo Explosions, and only that. The AIU does not have any other powers that can detonate or source such combos.
While playing my first game I was awarded several kills with a Cryo Explosion, which I can only source with all powers available to me. I obviously get more credit as a source (because I kill something: that is extra exp and counts towards medals), then the one who detonates. That is good for me, but not as good for the detonator. Does he get extra points for killing/damaging something with 'my' explosions?