Polyethelene pipe would come on really big reels as opposed to 10 or 20 foot sticks. It is not an approved electrical raceway so any conductor would have to be approved for direct burial. For example a conductor approved for a wet location can be installed in a pvc raceway like rw90, but rw90 is not approved for direct burial so it could not be installed in polyethelene. It is common for city utilities like the city of Calgary, to use polyethelene pipe to be installed by a direct burial tractor. One that trenches and buries in a single operation between light standards. It is popular because the pipe comes in 1000 foot reels, is very strong, and does not require couplings. The city utility can later install rw90 xlpe with a jacket (approved for direct bury) later.
In areas like Victoria with all the rock in the ground street lights are wired overhead and very few contractors use polyethelene pipe.
The advantage lies in the reduced burial depth required. A single conductor like rw90 XLPE with a jacket or nmwu has to be buried at 900 mm in a traffic area but can be burried at 750 in a polyethelene pipe. That and the fact that the wires can be changed in event of failure just like a raceway.
Polyethelene pipe is considered mechanical protection only and is not a raceway as it applies to table 53 or section 12