Even if you have a duplicate incoming supply it is almost certainly going to originate from the same local HV/LV transformer in the distribution network. In this scenario, duplication of supplies in suitable fire resistant wiring, such as high performance FP, or MICC (Pyro) would be perhaps the best chance. Feed each cable from different devices at the origin, take different routes to the lift. Ensure that the duplicate supply scenario is well documented and correctly designed. Ensure that the cable route is suitably protected and fire stopped. Ensure that the supply system is designed with full selectivity, thus should the circuit protection of the first supply (either one) fail it will not cause the main DNO protection to operate. This will allow the second supply to operate to failure. I personally would be pushing for MI (Pyro) and evidence of the adequate design in the form of calculations and selectivity studies. If you understand this, great, if not please ask away. If your contractor doesn’t, then find another one who does. You might need a competent designer to do the design and someone else to oversee the installation to ensure that it is done adequately. Let me know if that is the case & I can guide you further.