Fences, walks, etc., would fit under ancillaries.

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mechanical system,

Any building service using machines. They include plumbing, elevators, escalators, and heating and air-conditioning systems. The introduction of mechanization in buildings in the early 20th century brought about major adjustments; the new equipment demanded floor space, and the design team began to include electrical and HVAC (heating, ventilating, and air-conditioning) engineers. Heating and cooling changed dramatically. Modern buildings, with their large heat gains, turned central heating into little more than a supplement. Heat removal is a much more serious burden, especially in warm weather. The roofs of high-rises are occupied by cooling towers and mechanical penthouses; entire floors are often dedicated to the containment of blowers, compressors, water chillers, boilers, pumps, and generators.

https://www.britannica.com/technology/mechanical-system

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What are building mechanicals?
When referring to mechanical services within a building, this commonly includes plumbing, electrical systems, HVAC, ventilation, elevators, and possibly even escalators. If moving components are involved, such as water, electricity, or gas, it is most likely a mechanical system
https://www.mcintoshok.com/what-are-the-mechanical-services-...
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ESA generally does not inspect high-voltage equipment during their station inspections. Their focus is typically on building ancillaries, ground grids, fences, structures, environmental hazards, and vegetation management.
https://www.rds.oeb.ca/CMWebDrawer/Record/664716/File/docume...