The Spiny Plumes always aggros to the player with the 2nd most hate in my experience, which is usually the OT. What is random is the location the Spiny Plume appears and what can end up happening sometimes is, if the OT is slow to grab the Plume, the healer (for example) can end up grabbing hate. This can make it appear as though the Plume spawned with hate on somebody else, but it didn't.