We have 6-sets of 600mcm that are shown to terminate in an existing utility owned service vault(its more like a room with controlled access)There is an existing service that is already in this vault,the wiring method used was a wireway that dead ended and from there they supprted the conductors(exposed) with a piece of uni-strut as they went into the utility cabinet.Our situation does not allow us to use conduit it would be next to impossible,we were thinking as an alternative method,- using wireway with a transition to cable tray,however looking @ 392.3 (a) uses permitted,I dont see where we can install our "XHHW" conductors on open tray.We have inquired the local wiring inspector to pay us a visit,however I like to have a game plan to present to him,instead of just asking how-any thoughts?thanks.