Ask the contractor how they will do the job safely
The contractor should be able to explain a safe method for how they intend to complete the tree work. Safe Work Australia has a guide to managing risks for tree work that can help you understand if the indented work method described by the contractor is safe.
Contractors should check for hazards prior to commencing work. If you are aware of any dangers on your property that could cause harm advise the contractor, such as underground tanks, underground services (gas, electricity) or plumbing near the trees.