I find absolutely no excuse why an airport employee should ever have to pay for his/her own parking, regardless of what happens in other areas.
Airports generally are more remote, have less mass transit, and airline employees work shifts that make mass transit not a viable option. Further, crew members are often expected to show up at practically any hour of the day or night and leave their cars for days at a time.
And let's not forget that most airline employees don't make what many downtown workers make.
The only justifiable reason I see for airline employees to pay for parking is if the work in a downtown (or business district) building and generally work daytime hours. Some airlines even pay for parking for their employees in downtown/business district buildings but not during normal business hours (M-F 8-6).
And there are companies that provide mass transit benefits - either free or reduced - in part because there are often tax incentives to the companies to get cars off the road when they can.
In some cities where mass transit is available, it can be a far faster option that parking in a remote lot and riding a bus.
Kev,
are you saying you personally have ot pay for the 2nd tag for the 2nd car but the first one is free? Can you switch one tag between cars?