No, it is not recommended to tie off to an aerial lift. Aerial lifts are designed to support the weight of the basket and its occupants, but they are not designed to support the weight of a worker who is tied off to the lift. If a worker were to tie off to the aerial lift and then fall, the additional weight of the worker could cause the lift to tip over or to fail, leading to a serious accident.
What OSHA says
According to OSHA (Occupational Safety and Health Administration), using an aerial lift as a means of fall protection is not acceptable. OSHA states that employers must provide their employees with a fall protection system that meets the requirements of OSHA's fall protection standards for construction, which includes using personal fall arrest systems, such as a full-body harness and lanyard, when working at height. This information can be found in OSHA's Construction Industry Standards, specifically in 29 CFR 1926.502 (Fall Protection).
What IPAF says
The International Powered Access Federation (IPAF) also states that it is not acceptable to use an aerial lift as a means of fall protection. IPAF's guidance states that personal fall protection equipment, such as a full-body harness and lanyard, should be used when working at height. IPAF provides training and certification programs for personnel who operate powered access equipment, and fall protection is an important aspect of safe working practices covered in their training courses. For more information, you can visit IPAF's website and review their guidelines for safe use of powered access equipment.