No, they aren't free tickets. Employers can offer discounts to staff and as long as the cost of supply isn't more than the price the employee pays there is no tax implication. Hotlines aren't massive discounts, as long as they are above airlines cost base they are fine. For standby tickets as there is no guaranteed seat and it is not removing the airlines ability to sell a seat at full fare they would only need to cost enough to cover the incremental cost of food, fees, additional fuel etc.