The company does NEED probable cause, though. They can just demand that as a condition of your continued employment they get to search your vehicle. If you consent and have a firearm, and that violates company policy, then they can fire you.
If you have received a copy of the company policy, and it is written in compliance with PC 30.06, and the parking lot is posted as well, then you can be prosecuted for criminal trespass by a license holder, since you have received notice and the facility is posted (If the parking lot is not posted, you might maybe have an out, but I wouldn't bet my freedom & CHL on it).
If you are in a high-demand occupation, it may be worth your time to find an employer that isn't quite so rabid about it. Otherwise, it sounds like you may be S.O.L.
You may want to check the exact wording of the policy against PC30.06. If it doens't match up and the lot is not posted, you can't be prosecuted for having it in your vehicle (you can be fired, however).
If SB534 is passed into law & signed, they won't be able to fire you for THAT (but they'll likely find another excuse).
