In case anyone is wondering I got it working:
from objc_util import *
import speech
import time
AVAudioSession = ObjCClass('AVAudioSession')
audioSession = AVAudioSession.sharedInstance()
oldCategory = audioSession.category()
audioSession.setCategory_error_(ns('AVAudioSessionCategoryPlayAndRecord'), None)
speech.say('hello') #like a phone call
time.sleep(1)
audioSession.setCategory_error_(ns(oldCategory), None)
speech.say('hello again') # speaker phone