Who needs to contract?

[Andrea Finkelstein]

We own property with a commercial restaurant in downtown Phoenix. The tenant is having trouble with unauthorized day and overnight parking, as well as homelessness, drugs, etc. We've decided to work with a tow company as well as post the correct tow and no trespass signage (and work with police re non-vehicular trespass). The tenant lease encompasses the whole property including the parking lot. They initially wanted to work with a non-tow company that would charge those who park and I'm guessing pay the tenant something. But that would definitely be a sublease against our agreement. Can we, as the landlord, contract with the towing company, if for no profit or income to us? Or is that infringement on their leasehold rights? Can they contract directly with the tow company if no income comes to the tenant from it? Do we need an addendum in our commercial lease to do either? Thanks in advance!