Emergency evacuation and rescue procedures must be in place before the work starts. For example, how will you rescue a person who has fallen while using a fall arrest system? It is not acceptable just to rely on the emergency services. Rescue procedures need to be covered in the risk assessment and planned prior to the work activity being carried out.
This will require cooperation and communication between all parties including property owners and managing agents, window cleaning contractors and sub-contractors and their workers.
It is important not only to have these in place but also to check employee understanding of these procedures before beginning the work. For further information regards the importance of rescue see here suspension trauma