Can agencies charge owners storage/towing fees related to the seizure and prosecutor of their vehicle?

The only thing I could find in ch 59 is 59.06(2) which states that storage fees can be deducted from the balance of a sale of forfeiture property.

Is there any other statute or caselaw that governs this?

CCP Art. 18.23 is the only other thing I know of off the top of my head. It may or may not apply to your situation.

You need to tread lightly in that area. Asset forfeiture is intended to be remedial rather than punishment. That is the reason given by the appellate courts as to why a forfeiture is not a violation of the double jeopardy or excessive fines clauses of the US Constitution. If you assess storage either through the criminal case or by way of a civil proceeding you may fall into these constitutional issues. Example: You seize a vehicle worth $20,000 and the owner is placed on probation and ordered to pay $2,500 restitution for storage of the seized vehicle. Will an appellate court say that by charging the storage fee you turn the remedial seizure into a punishment of $22,500 when the maximum fine is $10,000? Just a thought.

There is an Attorney General's Opinion ooncerning this.