a way to counter he elephant would be a unit of skirmishers in front of another unit of quality skirmishers. the front unit gets close to the elephant and begins shooting... if charged by the elephant it evades through it's support, who cannot evade ( page 19, 4.7 final sentence). Since the supports cannot evade, and hence not caught evading, they should be able to fight. This is situational and may work if the support are Thracians with halberds.
I also assume that skirmishers cannot charge elephants, although page 39 " combat with elephants" suggests they can??