As an employee (middle management) at one of the big four national wireless companies, and one who is involved in cell site management, I cannot stress enough the tip from page one that 99% of the time we lease land from private property owners. That said, most of the towers are not held by the carrier, they're typically held by one of the big three tower companies (e.g. Crown Castle). Most of the lease space is fenced, which means you're not to be inside the lease compound. Other than that, it's a novelty to camp near a cell tower but you're on private property and subject to the risks that are associated with trespass. As a motorcyclist, only you can decide if the risk is worth the reward.