LISK is NOT released yet. period.
anything that is being bought/sold is just a promise out of thin air.
these exchangers might not even have enough LISK to cover withdrawals by the time of release and when anybody would want to withdraw what they have bought so far.
If they actually don't have the Lisk yet and needed to buy it to replace the IOUs, that would be very interesting, price-wise.
If you would find that out and made it public, yobit's only opions would be to buy Lisk at nearly any price, or take the money and run.