There is no requirement for the life system to be lidded.

A lid is effectively required only when using a cable protective system (an enclosure) as the means of achieving fire survival. Under BS 8519:2020, those protective systems must be fully enclosed (i.e dura steel); open-top (2- or 3-sided) systems are not permitted under BS 8519:2020  – appendix H ( these are referenced in The BS EN 1366-11:2018+A1:2021 but this standard is for laboratory test method for cable protective systems not applicable here)

Basically, when we’re using compliant fire-resistant cables on dedicated, independent supports, then BS 8519 does not require to add lids to tray/ladder.

Still, we must meet the survival time and the routing/separation/support recommendations, but a lid isn’t the mechanism that makes this compliant.

Utilities like UKPN or PowerON require Lid underneath for containment passing in BIN stores or BIKE stores to protect from potential mechanical damage.

Top lid is often used as mechanical and UV protection for cables on the roofs.

Hope that helps