In what country and what application? It probably would not comply with NEC in the US unless the cable was UL listed as MV cable for use in tray, which seems unlikely.
If you're a US utility, you can do whatever you want, without regard to NEC in substations and power plants.
Tray cable is tested for flame propagation and URD probably is not.
For NEC compliance it would also have to be isolated from any low voltage cable by a metal barrier.
Why Underground residential Distribution (URD) is proposed to be installed in cable tray?
Is the cable sunlight (UV) resistance rated?
Even if the cable tray system meet code requirement, URD cable installed in tray may not be the most economical choice since the concentric neutral can be saved if the metallic cable trays is permitted to be used as Equipment grounding conductor (EGC) where continuous maintenance and supervision ensures that qualified persons will service the installed cable tray system as stated in NEC Section 318-3(c).
DPC
It is in Canada
Need to carry neutral from main sub station to existing 25kv O/H ploe line. Because bldg is in the way, Cannot run O/H line all the way. So part of run is cable on top of roof.
Since hard to find 25kv 4C plus ground armour cable. Thinking to run URD in tray on top of roof.
JWA1
Who owns the cable? IF it's a utility and the NEC does not apply. I have seen try use in large vaults ( approaching swimming pools in size ) to support red stripe cable.
You might consider MC cable - metal-clad with continuous corrugated armor (Okonite C-L-X). It is made up to 35kV, includes ground wire and the armor sheath can be used as a neutral/ground. It is listed for tray use and for direct burial.
