Due to the release of ORAS, you can pick any unova starter after clearing the league again (I think it goes Sinnoh, Johto then Unova starters). Apparently you can get HA snivy from this, via soft resetting.
I got snivy myself, let's see if it can be HA too.
Well actually... I can't find any proof at all. Sorry about that, genuinely. A friend told me it was possible and he succeeded in getting a HA.