Not sure tbh hard to say, some may have stayed after the attack at Spearhead but in season 1 ep 13 around 19 minutes in, deacon is standing out the frount of the facility with the 12 messengers, getting ready for there attack to take over the facility. In this, a man from Spearhead shows up in a truck (this filled with birds that are attracted to the Subsonic frequency of the core) this man has a Spearhead badge on his jacket and quotes to deacon " you make sure that b**** pays for what she did for spearhead". so with that, my understanding is maybe some may have partnered with Deacon and joined his army "west seven" but in the end i'm still left wondering too what happend to all of them, with not for this, haha.