The train station manager is wrong.
According to the DMV website, once you have a valid DP placard, DP plates, or DV plates, you may park:
In parking spaces with the International Symbol of Access (wheelchair symbol).
Next to a blue curb authorized for persons with disabilities parking.
Next to a green curb (green curbs indicate limited time parking) for as long as you wish. There is no time limit with a DP placard, DP license plates, or DV license plates.
In an on-street metered parking space at no charge.
In an area that indicates it requires a resident or merchant permit.
I recommend that you go to the DMV website and print out the page showing where you can park and deliver it to the manager. You also should find out who his supervisor is and notify him or her of the problem (best if you do it in writing).
If you follow these steps, if he ever does tow your car, you will have a very good lawsuit.