'..However, a lifetime of field experience has shown that in some instances cleats may be required to ensure that the cables are in proper trefoil configuration and remain in trefoil configuration until the cables are covered with whatever fill is used'.
I have the following opinion.
1. Cable cleats are of very heavy mechanically strong design including usually anchored down on a fixed position. High cost ! , but it is mandatary when cables are on cable tray/ladder in free air.
2. To ensure that the cables are in proper trefoil..., needs very simple non-magnetic material or even plastic cable tie, to hold them together during cable laying. These are relatively simple very low mechanical strength and are very low cost. They serve NO purposes after cables are buried. Therefore, Cable cleats are NOT required.
3. Cable cleats and cable-tie are of entirely different mechanical strength/design and cost. They serve different purposes.
Che Kuan Yau (Singapore)